Few rivalries in sports fuel as much hostility and pressure to win like college football's annual Red River Showdown between Oklahoma and Texas.

And through the years, those monumental stakes have led to some serious skullduggery. The most notable example came in 1972, when the Sooners spied on Texas' practices, allowing them to block a quick kick the Longhorns had secretly been working on en route to a victory.

Now, thanks to Mike Leach, the 1999 game can officially be added to that same legacy.

During pregame warm-ups of that year's Red River Showdown, an underhanded script outlining OU's opening offensive plays was spotted on the field by one of Texas' student assistants, who scooped it up and took it to Longhorns defensive coordinator Carl Reese. To the heavily favored Longhorns, it seemed as if they'd caught an enormous break.

"We were trying to figure out if it was authentic," Reese said. "We were in this state of, 'Can we believe this?'"

They shouldn't have.

It was a fake, part of a plot hatched by Leach, the Sooners' offensive coordinator, and consulted by the Longhorns, who quickly fell behind 17-0 before realizing they'd been duped.

"That does sound like Mike," said former Texas coach Mack Brown, unaware of the script at the time. "I do know this: Offensive coordinators are so careful with those scripts they wouldn't be losing them. Those things are valuable. Only Mike would think to lay one out there as a decoy."

In his 2011 book "Swing Your Sword," Leach briefly mentioned the lark. But he never knew for sure just how seriously the Longhorns had taken it, how often they'd referenced it or just how effective it had been.

He was elated to learn recently that they had fallen for it so hard.

"These things evolve and become somewhat legendary," Leach said.

Leading up to the game, Leach didn't tell OU coach Bob Stoops he was planting it, and Reese didn't inform Brown he had it. As a result, few people on either side knew of the decoy script's existence. And yet, it nearly propelled the underdog Sooners, with Stoops in his first year and OU coming off a 5-6 season, to a victory.

"That game might've been the most bizarre experience I ever had as a college football player," said Ahmad Brooks, a starting defensive back for the Longhorns. "I can't tell you how wrong we were in the first three or four minutes with every playcall we had. I've never seen anything like it.

"It was complete pandemonium, and it was complete confusion."

Reese finally trashed the script, and Texas settled back into its game plan to rally and roll 38-28.

But not before Leach unleashed pandemonium upon the Longhorns for a quarter.

"It was a decent effort," Leach said. "But it would even be more legendary if we had won the sucker."

A decent effort, fit for such a heated rivalry.

"Yeah, it was kind of shady," said former OU tight end Trent Smith, whom Leach drafted to "accidentally" drop the sheet in front of the Texas coaches.

"But it's OU-Texas. There are no rules."

In his only Red River Showdown, Mike Leach, right, left a lasting memory for coaches on both sides. AP Photo/J. Pat Carter

On the Wednesday night of game week, Leach was with OU offensive assistant Cale Gundy when the two began laughing about how funny it would be to create a decoy script for the Longhorns.

"You start out kind of joking around about it," Leach said. "And then it's like, 'All right, screw it. Why not? Let's do it.' Then we had to think of stuff to put on it."

Leach didn't want to just mess with Texas. He wanted to use the ploy to gain an edge. So he took actual plays he had been planning to call and began doctoring up potential companions alongside them.

"In other words, with the fake playcall, we wanted to complement it," he explained. "We would run something that would hopefully attack the space that we created by what they thought the play was gonna be."

For the decoy script, Leach began inputting plays the Sooners didn't even have in their system. And he invented the terminology for them as he went along, balancing the line between too complex to understand and too simple to be believable.

GameDay at the Red River Showdown ESPN's College GameDay will be live at the Classic Corral from the State Fair of Texas in Dallas from 8-11 a.m. Central on Saturday.

"It had to look like our terminology," Leach continued. "But Z-25 Jet, they may not know what the hell that means, you know? But you didn't wanna get busted, either. So it had to sound football-ish."

When he'd finished his masterpiece, Leach put Gundy's name at the top of it, as if it were Gundy's copy of OU's offensive play script. Then, he had it laminated to make it look official.

"That's Mike," Gundy said. "It was funny."

Outside of Gundy, Leach kept the rest of the coaching staff in the dark, including Stoops, who was preparing for his first Red River Showdown.

"I figured Bob had enough problems and we'd let Bob just go ahead and deal with some Bob stuff," Leach said. "It was really me and Cale. You couldn't tell too many because if you did, the cat would get outta the bag or you'd have too many guys looking suspicious."

Next, Leach had to figure out how to lure Texas into taking the bait.

During the 1999 season, Leach, Smith and fullback Seth Littrell had a little tradition during pregame warm-ups.

"Back then, Coach Leach and me and Seth all dipped Copenhagen snuff," Smith recalled. "I would always carry the can out on the field during pregame. So I remember [Leach] calling me over and asking for the can. We were all going to take a dip together and he was like, 'All right, here's the deal, guys ...' explaining this to me and Seth. I just remember how excited he was about it. I got the feeling this was a total rogue thing that he was doing on his own.

"But he was like, 'Oh, this is going to be amazing. This is going to be hilarious. This is going to be epic.'"

As Leach carried on, Littrell and Smith grew just as excited.

"I thought it was pretty clever, to be honest," Littrell said.

"Yeah, it was kind of shady, but it's OU-Texas. There are no rules."

Leach then handed the script to Smith and ordered him to execute the plant, which he did to perfection.

"He says, 'I'm going to walk off. I want you to stand here for a minute. Then, I want you to drop it right in front of their coaches over there and then just keep jogging," Smith said. "It was kind of exciting. I act like I'm going to tuck this script in the belt on my pants. I let it fall and just kept jogging as though I thought I still had it.

"It was killing me not to look back and see if it had worked."

Off to the side, Leach kept the discarded script within his peripheral vision. To his delight, he watched as Texas student assistant Casey Horny picked it up.

"The body language was awesome. It was like watching a Muttley cartoon," Leach said, referring to the villainous 1960s dog who was the sidekick to Dick Dastardly. "They decided to give it the Muttley snicker and then went up the tunnel."

Former OU fullback Seth Littrell, now head coach at North Texas, was part of a small group of people who knew Leach's plan. Elsa/Getty Images

Back in the locker room, a few of the Texas coaches, including Reese, secondary coach Everett Withers and Tom Herman, just a grad assistant that season, passed around the script, attempting to determine what to make of it.

"It was one of those deals where we were like, 'No, this can't be real,'" said Withers, now head coach at Texas State. "But we all kind of thought it was."

They ultimately decided not to go to Brown with it. Instead, Reese took the script with him up to the press box.

"That's when I really looked it over and we talked a little bit about it," Reese said. "Everybody really thought it was the real deal."

Reese began tweaking his defensive calls to match the script. And it wouldn't take long for that to backfire.

"I just remember sitting in the huddle that first drive and kind of giggling," Littrell said. "Like, they think they know what we're fixin' to do."

The second play of the script called for something akin to a double-reverse pass. In response, the Longhorns brought Brooks on a nickel blitz with the goal of sacking the Sooners for a big loss.

Instead, Leach snuck freshman receiver Antwone Savage behind the linebackers on a shallow crossing route going the other direction to the right. Quarterback Josh Heupel found him so wide open that Savage galloped untouched for a 44-yard touchdown.

"We thought maybe we just screwed the verbiage up," Herman said.

So despite getting torched for a touchdown in two plays, Texas didn't immediately give up on the script. In turn, its defense grew only more discombobulated.

Reese was concerned about all the screens on the decoy script. So when he otherwise would've brought pressure, he sat back, giving Heupel ample time to pick Texas apart. According to Withers, the Longhorns were also unsettled by all the wrinkles in the script they hadn't prepared for, such as backs going for passes out of the backfield.

"We were so worried about it that we weren't worried about just doing our job," Withers said. "It captivated our attention, and it was probably the reason they were so effective in the first quarter."

When the Sooners went up 17-0 just 10 minutes into the game, Reese finally scrapped the script.

"It was tossed into the trash can," he said. "At that point, you thought you'd been had. I just got back to the basics and started looking at what was really going on and trying to adjust to it."

That's all the Longhorns really needed. They dominated the rest of the way, picking off Heupel three times, including once by Brooks.

"The thing you didn't want is those Longhorns just triggering at you full steam without any hesitation," Leach said. "Because they were pretty overpowering at that point."

They indeed overpowered the Sooners to complete Texas' largest comeback in 34 years. The Longhorns held them to just one more touchdown, which didn't come until late in the third quarter after Texas had built a 31-20 lead.

"When it was all over with, I had a good laugh," Reese said. "Because it really was a nice ploy, and it did a good job of messing us up for a while.

"I learned a good lesson there."

Oklahoma quarterback Josh Heupel threw 44- and 30-yard touchdown passes in the first quarter before the Texas defense shifted gears. Andy Lyons/Getty Images

After the game, the Texas assistants were suspicious that Leach had been the one to plant the decoy script. But they weren't positive.

"I had thought, based on his reputation -- I mean that not negatively at all -- but that it was certainly something that he might do," Herman said. "I don't know that I ever got confirmation until I talked to somebody who was on the Oklahoma staff, and they adamantly confirmed, 'Oh yeah, that's something he was working on all week.'"

Brooks, meanwhile, said he and his teammates remained mystified as to why their defense had looked so lost that first quarter.

"The funny part is, I didn't hear that story until Tom told it a year ago," he said. "The coaches never tipped us off that that had been found, so we had no idea.

"It was a brilliant move by Mike Leach."

As for Leach, he'd never been told of Texas' account of the event, either.

"Was Herman there?" Leach asked, before being reminded Herman was an assistant then, after which he perked up. "Oh, so what did he say? I've never heard their side. What did he say happened?"

For Herman and the eight other assistants or players in the game who would go on to become future head coaches, it was a valuable reminder that something that seems too good to be true probably is.

"Hey man, they shouldn't have been trying to cheat," said Littrell, now head coach at North Texas. "That's why they got duped."

Knowing the fruits of his efforts, Leach obviously doesn't feel any shame. Only more pride.

"Well," Leach said, "nobody said you had to pick it up and read it.

"It's like, listen closer in your Sunday school lessons, and it probably wouldn't have come so easily for us."