Stan Lee's voice and likeness being used for Senator Lieber allows for a scene where, if you have Deadpool on your team, creates a humorous bit of dialog. Deadpool seems to recognize Lieber as Stan Lee, but Lieber denies this. This is actually a reference to the Deadpool comics where Deadpool actually seems to be aware that he is a fictional character in a comic book.
If player one is Spider-Man with the conversation with Senator Lieber (aka Stan Lee), the senator will rebuke Spidey's claim of being an ordinary guy and state that he's "more amazing or spectacular," a reference to two different series of Spider-Man comics.
Although Stan Lee has provided his voice for several Marvel video games, usually as a narrator or announcer, this would mark the first time he's provided the voice of a character within the game.
This game integrates two Marvel Comics storylines into the plot of the game, Secret War, and Civil War