WrestleMania 34 is now, quite possibly, the most stacked card in the history of the WWE.

Roman Reigns battles Brock Lesnar for the Universal title, AJ Styles and Shinsuke Nakamura will clash for the WWE title, John Cena will face the Undertaker, Triple H and Stephanie McMahon will tag against a debuting Ronda Rousey and Kurt Angle in addition to the team of Daniel Bryan and Shane McMahon battling Sami Zayn and Kevin Owens.

That's literally just scraping the surface. There's a triple-threat for the Intercontinental title, a fatal four-way for the U.S. title and much, much more.

But, knowing the WWE, there is always a surprise or two on the Grandest Stage of Them All.

Last year, the Hardy Boyz made a dramatic return to the WWE and won the Raw tag team titles, so what this year?

According to the bookmakers, the Rock is 1/100 to make an appearance at WrestleMania and he might even wrestle.

"The Rock is still one of the WWE's biggest names and an appearance from the Great One would spike interest and generate huge publicity for Vince McMahon's business," said Oddschecker spokesperson George Elek. "The bookies believe he is almost certain to appear once again at The Showcase of the Immortals and 1/100 implies a 99 percent chance that we will see The People's Champion inside the Squared Circle."

The 45-year-old is 25/1 to compete and although that might seem high at a glance, in previous years it's been nearly four times higher.

Only a few months ago, Roman Reigns addressed the idea of facing the Great One at the WWE's showpiece event.

"At the end of the day, I know it's a money match. And I'm the guy who is still in the ring, so if someone who isn't in the ring every single night wants to come back in the ring, we now call it my yard, so he is going to have to come to me and then we'll go from there. It won't go down anywhere other than a WWE ring, that's all I'm saying. If he wants to get it, then I'm not stepping back for anybody."

"We represent the same family tree and having the opportunity to represent our culture, there would obviously have to be a sit-down and we would have to express how we feel and the light we want to do this in ... because there's a lot of people we represent watching. The last thing I want to do is make it confusing or anything like that."