I knew he looked familiar, but I just couldn't place him. Considering Hulk's voice is Lou Ferrigno, I was trying to think of everything Hulk related, from the movies to tv shows and such and didn't even consider that angle.
Someone mentioned the old guy that finds Banner after his first episode: He was in Alien and asked if Banner was an Alien. I call that an Easter Egg.
As far as Thanos, he has an interesting story but the only thing involving him that I liked was a Deadpool storyline where Thanos curses Wade to basic immortality as a punishment for stealing Death's affection from him. Beyond that, I won't deny there is potential there, but it'll take a lot to flesh it out. And a few Hulk scenes. God those scenes are still making me laugh.