The morning of the weirdest day of David Mitchell's life began with a shrill beeping sound. David groaned, cursing Victoria's habit of messing around with his phone as he groped around on the bedside table. He heard several items crash to the floor and the beeping mercifully stopped. David groaned again, cracking his eyes open and wincing as the morning sunlight hit him. Why had he not pulled the curtains last night? Thoughts still sluggish, David looked around the room with growing confusion as he realized that this wasn't his bedroom. Nor was it his guest room where he sometimes retreated with Barb when she was having a particularly fussy night and he didn't want them to disturb Victoria. But Barb wasn't here anyway, Victoria and her mum had taken her up to Scotland for a long weekend. He blinked at the unfamiliar surroundings, this was... definitely not his house. Huh.

He tried to cast his mind back to the previous night. With a jolt he placed his surroundings, this was Lee's room! His actual bedroom, not the guest room that David had occasionally stayed in in the past. Right, he'd spent the evening with Lee because Tara and the kids were also out of town and Lee had called David up and suggested they spend the evening 'reliving the glorious freedom of bachelorhood.' David didn't actually miss his single days (and he doubted Lee did either) but the prospect of pizza and uninterrupted conversation and maybe a movie rated above G sounded good, as did getting out of his temporarily empty house. So he'd shown up at Lee's with a bottle of wine (so he wouldn't have to drink Lee's shitty beer) and they had eaten and chatted and watched a terrible movie and raided the cupboards for sweets and chatted some more. David didn't think he'd gotten too drunk to drive home, and in any case if he'd stayed over because he wasn't safe to drive it wouldn't have been in Lee's bed.

With a sudden jolt of horror he jerked his head to the side, but the other side of the bed was blessedly empty. Anyway, he reminded himself as his heartbeat slowed, if they both got pissed and passed out together it would have been in the living room. This made no sense, why was he here? And where was Lee? David rolled out of bed, intending to go in search of his friend, but was brought up short looking down at his own body. The faded Blackburn Rovers t–shirt and threadbare checked pyjama trousers weren't familiar, and something else looked wrong, but it was too weird, so he focused on the sleepwear. He must have borrowed them from Lee, but why couldn't he remember...

David shook his head and detoured to the bathroom on the way to find his friend. In the bathroom he gave a start, looked wildly around for Lee, caught sight of Lee in the mirror again, spun around twice more, screamed a bit, and finally sank to the floor clutching his face, and trying to stave off the panic attack he could feel building because this was 100% not possible so he had to figure out what was going on, and he could not do that if he was panicking.

The sudden sound of an obnoxiously tinny rendition of some pop song David vaguely recognized broke through his attempts at breathing deeply and not thinking too hard. He scrambled back into the bedroom groping around the pile of things he'd knocked off the nightstand, bypassing the ancient alarm clock and finding the smartphone beneath. He jabbed the answer button and held it up to his ear.

"Hello?" he winced at the unfamiliar sound that emerged from his mouth.

"David, is that you?"

Ooh, that was weird, the voice from the phone sounded just like he did on recordings. David winced again.

"Um..."

"David? It's Lee, come on, who else would be answering my phone right now?"

"Oh my God, Lee! Where are you? What's going on? Why am I–"

"David! David, calm down. Deep breaths David okay? In... Out... That's good, just relax and tell me what you remember about last night."

By focusing on Lee's voice and studiously not thinking of anything other than the questions he was asking, David managed to calm himself enough to answer in a more normal tone of voice.

"Last night?"

"Yes, last night. For example, do you remember where you fell asleep?"

"Well I thought in my own bed, I mean we didn't get that drunk, and I thought I left at a reasonable hour?"

"Yes, that's what I remember too, and you said I could come with and use the guest room if I wanted a shorter commute this morning, but I said no thanks, because I hate your guest bed."

"And I made a stupid joke then went home."

"And nothing weird happened on the way home?"

"Like what?"

"I don't know!"

"No Lee, everything was perfectly normal. I got home, fed the cat, cleaned my teeth and went to bed. Everything was fine until I woke up here as you!" David could hear the hysterical edge to his voice, but if there were ever a situation that called for hysteria this had to be it.

"Calm down David–"

"Calm down?"

"Panicking won't solve anything."

"And what will!?" David's voice climbed to a near scream.

"I don't know!" Lee sounded ruffled for the first time. In David's voice. It was too weird. "I don't know David, just... okay... we're due on the WILTY set in a couple of hours. I'm going to leave now, meet me in your dressing room as soon as you can yeah? And we'll go from there."

"Okay," David took a deep breath, "Okay, yeah we'll meet in my dressing room, and then..." he trailed off, what would they do then?

"David?" his own voice came through the phone, "David don't think about it now, just get dressed and meet me at the studio."

"Okay," David whispered hopelessly, and hung up.

Two hours later saw David hurrying into the BBC Studios, looking around anxiously in case he ran into anyone who would recognize him. Or rather Lee. But he was early enough that the building was all but deserted and he reached his dressing room without incident, tapping lightly on the door and whispering "Lee, it's me D–"

The door burst open, "Don't call me that!" Lee hissed, yanking David inside and slamming the door shut in one motion.

They stared at one another.

If David had thought about it, rather than resolutely not thinking about it, he might have thought there was no experience weirder then looking in the mirror and seeing Lee's face looking back. But he would have been wrong. This, now, seeing his own face in front of him, making ever–so–slightly the wrong expression of shock and confusion was... way weirder.

David whimpered and sank to the floor starting to hyperventilate for the second time that day.

"Breathe David. Come on, not again, if you pass out then I'll really start panicking, and then where will we be?" Lee's voice was simultaneously soothing and confusing. He sounded like David, but the cadence and words were all Lee.

David took a breath and looked up, shuddering but managing to make eye contact.

"Back with us? Okay, good, so here's my idea..."

Fifteen minutes later David was still arguing.

"No Lee! Absolutely not, we can't tell anyone! Do you know how crazy this sounds! I mean maybe we are crazy! I mean this can't actually be happening. Maybe this is all in your sick mind,"

"My–"

"And this is all a dream, or you're in a mental hospital somewhere,"

"I'm not–"

"Or maybe we're both hallucinating and everything is actually perfectly normal, I mean it's not like we've talked to anyone else–"

"David!" Lee shouted, "I don't care what you say or how much you object we are completely and totally unprepared to deal with the situation on our own, so I am going to call my mate whatever you say. He will not think we are crazy or hallucinating. Just because all your friends are boring..."

"Hey–"

"Victoria knows him too," Lee adds, feigning casualness, "Shall I call her for an endorsement?"

"No!" David's heart nearly stopped, "You can't tell Victoria!"

"Then let me call my mate. No offence David, but we are woefully out of our depth here, we're going to have to tell someone eventually."

David sighed gustily. "Fine."

He stared suspiciously as Lee dialled and waited for his friend to pick up. Unfortunately after the initial explanation Lee's side of the conversation was mostly non-committal noises that didn't give much away. So when he hung up, David practically pounced on him.

"What did he say!?"

"He's seen the sort of thing before,"

David felt boggled and relieved at the same time.

"And he'll make a couple calls and get back to us. But he says it usually wears off in 12 to 24 hours so we should just lay low for a bit."

"Lay low..." David echoed, "Lee, we're doing a show in," he checked his watch "Three hours! What are we going to do?"

"We'll do the show," Lee replied as if it was obvious.

David gawped at him.

"Come on David, we've been doing this show forever, surely we know each other's shtick well enough to fake it for one show."

As if to underscore Lee's point, David heard a door slam in the distance and the sound of voices nearing and then retreating as the speakers turned down another corridor. It was definitely too late to feign illness or come up with some other excuse. They really had no choice.

"Alright," David said fatalistically.

"Come on, how bad can it be?" Lee asked. "At least it will keep our mind off things for a bit," and he grinned.

"Somehow I doubt it," David sighed, resigned.

This was a terrible idea, David thought, sitting on the WILTY set between Rhod Gilbert and Hugh Dennis, Lee's team, which he had nearly forgotten to acknowledge when Rob introduced them. Lee, sat opposite him between Jack Whitehall and Bob Mortimer, had also paused just a bit too long when Rob introduced David's team. It was a miracle that no one had noticed anything fishy so far, but the show had barely started, and, oh God, the next home truth was for David, i.e. Lee.

"The first time I was left completely alone with my daughter, my wife arrived home to find the nursery wrecked and us both in tears," Lee read in David's voice.

He better not think that's true! David thought to himself angrily, nevertheless curious about the story Lee was about to spin.

"How old was your daughter?" Hugh asked from David's left.

"And infant?" Lee feigned confusion, "I don't know, quite small and still needed to be fed every hour, that was actually the problem."

"So what happened?" David asked.

"T– err Victoria wanted to meet an old school friend who was in town for a few days. We were already supplementing Barbara's diet with formula so it should have been fine, but I heated the formula too much I guess and A– er Barb didn't like it and started crying and worked hi– herself into such a state she threw up all over me, and then while I was trying to clean that up, she had an issue erm, lower down. So when T– Victoria arrived home we were both covered in puke and baby poop." There was a beat, "and crying," he added as an afterthought.

David was pretty sure Lee was talking about an actual thing that happened to him although he'd not heard the story. Lee could be oddly insecure about his parenting, which David had never understood because he was so obviously a great dad.

"So how did you wreck the nursery?" Rhod asked.

Lee had clearly forgotten the original statement, but recovered well, "I don't think you understand the volume of disgusting substances an infant can produce."

Both Hugh and Rhod thought it sounded true, so David sided with his team, even knowing it was wrong. Hopefully no one but David noticed that Lee was as surprised as anyone else when it turned out he was lying.

They got through the next few home truths without incident, both David and Lee doing the minimum amount of talking they could get away with. There was a weird moment after Rhod read out his truth (My nickname in school was 'Diminy Blunket.') when Rob invited Lee's team to comment, before quickly correcting himself. It wasn't a particularly surprising mistake, but tense as he was, David jumped a little although Rob didn't notice since he'd been looking at Lee the entire time.

It wasn't until Rob announced the mystery guest that it occurred to David that they should maybe have briefed each other on this bit. The week's guest knew someone on Lee's team, so he had no idea what was coming. Unfortunately he was also stuck playing Lee, so all he could do was hope that the person the mystery guest knew wasn't Lee. And frantically try to think of a Lee-worthy story to tell about the guest.

"Today's mystery guest is Tara," Rob announced, and a tall blonde woman walked on stage.

David groaned internally, he'd been hoping for a man he could claim to be Lee's bin-man. The woman was far too elegant for that to sound plausible or properly funny. Maybe he could pretend she knew his wife? They share a name, there ought to be some humour there...

A sudden bolt of panic shot through him and he quickly looked up at Tara to assure himself that she wasn't Lee's wife. But of course that would be stupid, he reminded himself, too many people would recognize her.

"Lee, what is your relationship to Tara?" Rob asked.

David nearly forgot he was being spoken to, but managed to respond before anyone but Lee (who was glaring at him) noticed his lapse. He still didn't know what he was going to say, but he was a professional comedian, and had worked with Lee for a decade, so he just opened his mouth and went for it.

"This is Tara, one time I accidentally stole her purse at a concert."

Rob moved on to Hugh, who claimed that he and Tara were old schoolmates, and David started mentally constructing his story.

Lee, bastard that he is, decided to question David first, with an evil glint in his eye that said that he was actually enjoying himself.

"So Lee," he said mimicking David's precise intonation so perfectly David couldn't help but feel he was being made fun of, "How do you accidentally steal a purse?"

"Well," David began, leaning into Lee's accent a bit, two could play that game after all, "Tara is also my wife's name, and the concert was in a venue that was particularly touchy about bringing in bags–"

"What was the venue?" Lee interrupted.

"A concert hall," David suppressed a smirk, the joy of working opposite Lee, and the challenge of playing him to him finally beginning to override his nerves about the whole ridiculous situation, and he warmed into a classic Lee deflection routine.

"What concert hall?" Lee presses.

"A big one."

"Which big one?"

"A London one."

"Which London one?"

"A London concert hall, yes."

"But which London concert hall?"

"The Royal Albert Hall," David finally answered.

"Thank you," Lee said with exaggerated politeness, "You may continue."

"Where was I?"

"At the Albert Hall," Rhod reminded him helpfully, and the audience laughed appreciatively.

"Oh right, well Tara's—my wife Tara's—purse was a bit on the big side, and I guess Tara's—the guest Tara's—was too, because both of them had to leave their purses at coat check. And then, after the show, I decided to be gallant and fetch my wife's purse for her. And of course coat check was a madhouse, with attendants just calling out names and not bothering to check tickets, and at one point an attendant called out 'Tara' and I just grabbed the purse without really looking at it."

"When did you notice your mistake?" Lee asked.

"When I got back to my wife and she said 'honey that's not mine.'"

"And how did you return it to the correct Tara?"

"Well my wife says it's not hers, and then I look down and realize she's absolutely right, I've never seen this purse before in my life, and then I look up and there's Tara—not my wife Tara—out of breath, obviously having chased me all the way from the coat check, so I say 'this must be yours' and she takes it from me, still too breathless to speak, but if looks could kill..."

Lee gave an unexpected, and not particularly David-like, snort of laughter.

David continues, "And my wife turns around and says 'you'll have to excuse my husband, he's colour-blind,' and Tara gives a confused sort of nod and leaves.

"Are you colour–blind?" Bob asked curiously.

"No!" David exclaimed, "She says she didn't know how else to explain my accidentally grabbing a bright green purse instead of a black one!"

Everyone laughed and Rob made them move on to the next story.

David managed to avoid saying much of anything throughout Rhod and Hugh's stories, and was only required to laugh along during the reveal (Tara is indeed an old mate of Hugh's, and apparently they used to be quite the little terrors in Primary School).

David also made it through the quick-fire lies without incident, heaving an internal sigh of relief as Rob read out the final scores. As soon as they were released David was off like a shot, even though he knew it was out of character for Lee, who liked to hang about and be friendly with cast and audience members alike. He ignored Rob calling after him, or maybe he was actually calling Lee, David felt totally mixed up after an hour of answering to Lee's name and preventing himself from reacting to his own. He dove into his dressing room, finally feeling able to relax slightly as the door swung shut behind him. Alone at last.

A moment later David realised that he instinctively went to his own dressing room rather than Lee's as he really should have. Good thing he got out before everyone else and no one saw him go into the wrong dressing room. I should leave now though, before anyone does notice, David thought hazily, but I feel so weird. He was suddenly gasping for breath even though it didn't feel like another panic attack. He staggered across the room to his dressing table, groping for the chair as dark spots danced before his eyes. He heard a crash distantly and thought maybe he heard Lee's voice but the world tilted and went dark before he could follow up on that thought.

With a feeling disturbingly reminisce of that morning, David came to with a groan, wondering where he was this time. Slowly his vision cleared and he realised that he was lying on the floor of his dressing room staring at the wastebasket by the door. He groaned again and slowly pushed himself up to sitting.

He heard a moan not his own, and looked up. Lee was propping himself up on the overturned dressing table chair. It took a moment to sink in because Lee looked so much the way David was used to see him, but then he shouted wordlessly, shooting to his feet, clutching his head at the sudden vertigo as he peered frantically into the mirror above Lee's head. His own face looked back at him, pale and horrified, but undeniably his own.

"Lee, Lee, look! Look! We're back!" he exclaimed, grinning maniacally.

"See, told you it could wear off on its own," Lee croaked, looking slightly woozy but grinning nonetheless.

There was a sudden knock on the door. Lee scrambled to his feet and David hurried to right the fallen chair, before turning to open the door.

It was Rob.

"Everything okay in here? I thought I heard something."

"Lee's just a klutz and knocked over my chair," David said, trying to sound unworried.

"Okay then," replied Rob, "Well, glad to see you're back to yourselves," and he winked before leaving, pulling the door shut behind him.

"Did he–" Lee began.

"No! He can't have–" David interrupted.

"But it sounded like–" Lee protested.

"No, just, no. It breaks my brain just thinking about it," David said firmly. "Rob does not know anything, it was just an unfortunate turn of phrase. Now, I am going to go home and pretend this entire day never happened. I suggest you do the same."

Lee opened his mouth, closed it, opened it again, "Fair enough."