Punisher, The

At the beginning of the Stark Towers level when the Yakuza start their attack, the scientists working behind the glass talk about an interdimensional portal, and one refers to the other as Doctor Freeman. Gordon Freeman is the main character in the popular Half-Life game series by Valve Software.

Go to any laptop during the game and look directly at the screen. The figure of the hulk appears flexing.

During the Stark Towers Level Iron Man arrives and destroys a helicopter that begins shooting at The Punisher while he is crossing a bridge. Iron Man then flies away around a building. Later on after completing the level, Iron Man talks to two of his guards.

Wilson Fisk, aka The King Pin, arrives to talk to the Punisher for a brief moment during the Fisk Industries level. He also appears in a movie after the game is completed.

Beat the Grey's Funeral Home level.

Beat the Chop Shop Level.

At profile name entry, enter WOODCHIPPER.

Part way through the Grand Nixon Island Level Nick Fury arrives and joins up with The Punisher for a period of time.

Beat the Lucky's Bar level.

If you choose to side with the Mafia at the slaughterhouse, when you get to a certain point you will hear two men. One will say "Damn they killed Ernie!" The other will say, "First Bert, now Ernie. We'll get those bastards." Bert and Ernie are the names of Sesame Street characters.