The end credits scene for Big Hero 6 has found its way online in a featurette featuring Stan Lee talking about the film. As you know, Lee was introduced in the film as Fred's dad in a family portrait. The video also includes a little bit of the end credits sequence that I will explain below.
For those of you who haven't seen the end credits scene yet, here's a brief description.
After the credits roll a potential sequel is set up, and as it turns out, Stan Lee may play a bigger part in the story. Fred, who is played by T.J. Miller, walks into his house missing his family. As he explained in the movie, they are always away on their special island. He walks over to the family portrait with Lee as his dad and touches it. When he does this, a secret door opens up and Fred walks in. It is there that he finds out his parents are superheroes. At that moment his dad, who is voiced by Lee, walks in and tells him they share the same attitude when it comes to laundry. They hug and the scene ends with Fred's dad telling him they have a lot to talk about.
You get a little glimpse of this scene in the video below thanks to Mashable. It would be so cool to see Fred's dad have a larger role in a sequel (if Disney plans on making one).