John Cena in Thor: Ragnarok
Article from cosmicbooknews
If we are to go by the IMDb listing for Thor: Ragnarok, WWE Superstar John Cena has joined the cast which is in part adapting the Marvel Comics Planet Hulk storyline.
So who is John Cena playing? Why it’s himself.
I can actually see John Cena making a cameo as himself in the gladiator arena. While we don’t know specifics about Thor: Ragnarok, I’m guessing Jeff Goldblum’s Grandmaster kidnaps various “champions” from around the universe to do battle and compete in the arena (nod to the original Contest of Champions Marvel comic book event). It’s possible that since John Cena is a “great” champion, that he gets picked for the gladiator arena and is featured in a scene. This also explains how Hulk gets taken off of Earth, as the Hulk would be considered a great champion, and how Thor makes his way to the arena.
source: The SpOTLight