After the latest episode of Castle, an interesting promo for The Avengers ran in the credits. It features Robert Downey Jr. having a bragging contest with Nathan Fillion. Now, Disney owns both Marvel Studios who is behind The Avengers and ABC who is behind Castle, so this might just be a clever little piece of cross-promotional marketing. However, rumors are flying that it might indicate just a little something more.

Marvel Studios President of Production Kevin Feige has been heavily teasing an Ant-Man movie in recent interviews. In fact, Feige has strongly hinted that Ant-Man could be one of the very next movies to be announced as official by Marvel Studios. While Marvel Studios isn’t going to comment on casting for a movie that they haven’t even officially announced yet, fan speculation has heavily centered around Nathan Fillion playing Ant-Man. Joss Whedon even joked at Comic-Con a couple years back that Nathan Fillion would play Ant-Man in The Avengers.

While fans don’t always get what fans want, the Mouse is likely grinning ear to ear that fans happen to want someone with which they have an existing relationship. The other question that springs to mind is when did Robert Downey Jr. and Nathan Fillion get together to shoot this promotional video. As everyone knows, Downey Jr. recently revealed that they shot a bonus scene for The Avengers after the world premiere. It’s widely assumed that the bonus scene will run in The Avengers credits, just like this promo ran in Castle’s credits.

Also, much speculation has centered around the introduction of Ant-Man being the subject of the bonus scene. Could Robert Downey Jr. and Nathan Fillion have been together for an Ant-Man bonus scene and then shot the Avengers promo afterwards? When you hear the two argue back and forth, Robert Downey Jr. finally trumps Nathan Fillion with the announcement “I’m Iron Man, and you’re not.” If you listen hard enough in your imagination, you can almost hear Nathan Fillion reply “Yeah, but I am Ant-Man.”