5 Jon Bon Jovi Is A Fan Jimmy Smits: Jon Bon Jovi was a humungous fan of the show and he came on to do a cameo for two episodes. I got to meet him a month before in Philadelphia, there was a concert and I actually introduced him – it was the first time I felt like what a rock star feels like. After we came off stage we went to his bus and he had made these "Matt Santos for President" t-shirts. He was loving the show!

6 Everybody Loved Allison Janney Martin Sheen: You know, there was a survey done and all of us, all the players, were interviewed and we were asked, confidentially, who we thought the best actor on the series was. As long as we were assured it was confidential we all gave our opinions, which would not be made known until after the series ended. Without a dissenting opinion, the entire cast voted Allison the very best among us. She didn't know it and none of us knew that we'd all voted for her, but she was considered the very best.

7 Moira Kelly Isn't Lost In Mandyville Moira Kelly's Mandy Hampton makes an unexplained disappearance between seasons one and two, with the fate of the character never explained or referred to. Among West Wing fans, the term 'going to Mandyville' became a euphemism for characters who dropped off the show's radar for no particular reason and would later be applied to the likes of Emily Procter's Ainsley Hayes, Matthew Perry's Joe Quincy and even Rob Lowe's Sam Seaborn (it's never explained why he doesn't return to the White House after his unsuccessful congressional campaign). In Mandy's case, though, it was simply because the character didn't gel with the show. "By mutual agreement we let Moira Kelly go after the first season," says Sorkin. "Moira is a tremendous actress and it was my failing alone that her character didn't work out. It had been my intention to explain her absence in the second season premiere but I couldn't find a way to do it that didn't seem like a naked bulletin to the audience."

8 Aaron Sorkin's Biggest Regret Was Losing Ainsley Hayes Aaron Sorkin: I made a mistake with Emily Proctor. I loved her on the show and when I had a chance to lock her up as a series regular I didn't take it. Being conscious that I already had eight mouths to feed I didn't want to be obligated to have the character in every episode, which I know now wouldn't have been an obligation, it would have been a gift. And of course Emily was snatched up right away by another show – CSI: Miami – and of course it was a giant hit. I made plenty of mistakes on the show but none of them that big.

9 Allison Janney And Emily Procter Discovered Twerking Emily Procter: Allison and I had this dance that we would always do. I had seen this weird clip of footage and I told her, "Allison, that dance, it's so bizarre. This is what the girls dance like." She was like, "What is that?" and I was like, "I don't know." Then in the last year, I was like, "That dance was twerking!" So Allison Janney and I had little twerking moments in our office. We were groundbreaking.

10 There Was More Than One Gail The Goldfish Allison Janney: I told everyone when Gail showed up, I said, "I know Gail's going to be with us for the run of the show, so I don't want to ever know if there is another Gail." So as far as I was concerned there was one Gail for the whole show. Thomas Schlamme: There were like fifteen of those goldfish, which Allison thought was the same one. It's like the first time you got a goldfish for your child, you run to the fish store and go, "Here's a dead fish. Can you give me one that looks exactly like this?" And then you put the fish back in the bowl. That's what happened. That fish would die constantly. To say that no animals were harmed in the production of the show was just not true. Those things just don't live that long! But honest to God, Allison still believes it was one fish the whole time she was there.

11 The Sopranos Was The West Wing's Nemesis Rob Lowe: The Sopranos was the Manchester United to our Chelsea. It was great to have them there, because it inspired everybody. That show's extraordinary; it's my second favourite TV show ever made. Can you imagine what The West Wing could've been though if we had the same luxuries that David Chase and HBO had? If Aaron said, "I'd like to be in a villa for a year in Italy and then when I'm done eating pasta, I'm going to come back and we're going to start up again." Can you imagine? Or if they'd let Aaron write a script that was as long or as short as he wanted it to be? Or if they said, "Aaron, how many do you want to write this year?" "You know what? I think I'd like to write ten." They're like, "Great!" No, we made The West Wing under the creatively crushing stipulations of network television and that it not only competed but excelled against cable is amazing.

12 Richard Schiff Giggles. A lot. Richard Schiff: It became tradition on The West Wing that whenever there was a very difficult scene and I was on the edge of that emotional line, if something messed up, I would go over to the other side and go into a giggling fit for about 45 minutes. The first two or three years the crew would always be entertained by it. But I was costing the production tens of thousands of dollars trying to get myself together and by the third or fourth year, people would groan whenever I started giggling, but it didn't help. Ninety per cent of the time it would happen with Martin, because words that were sometimes not English would come out of his mouth. One time in a very intense scene, he turned to me and said, "What do you think, Tobol?" I was gone for forty minutes. Another time was when Zakes Mokae was on our show. It was a very tough scene, my God – he played the leader of an African nation who was going back to his imminent execution! But Martin and he had to speak French to each other and Martin's French sounds a little bit like emotional Hebrew. I had to leave the room and they just kept shooting.

13 The West Wing Had An Unofficial Reunion Episode

Allison Janney: The last time we were semi-assembled was for Mary McCormack. Her sister was running for State Supreme Court in Michigan and we recorded a PSA-type video for her. It was so much fun to all be together again. It felt so easy, I mean I've spent more time with these people than with my own family. I'm not even kidding! We slipped straight back into it and did a whole walk and talk. I don't know if it was a result of the video but she won!

14 Yo-Yo Ma Does Indeed Rule Bradley Whitford: Dulé Hill is an amazing tap dancer. He started in Bring In Da Noise, Bring In Da Funk on Broadway. When we were shooting Noël, Yo-Yo Ma comes out and starts improvising on his cello and Dulé gets up and starts tap dancing. With Yo-Yo Ma! Dulé Hill: I did. There's video out there somewhere, I think I have a VHS of it. He was playing one time and I just started to dance with him. It happened organically. There was a camera there and Tommy Schlamme started to roll, but they didn't do the sound. But there is footage of me dancing with Yo-Yo Ma. It was a really special moment.