In the first level, just before you find the helicopter, you will have to push a wall down on three enemies. Two of them will get crushed. The last will start saying something like "me alive, me alive" before wolverine jumps down on him (notice the enemies big eyes) This is a reference to the Crash Bandicoot series, when either Crash, Neo, or a random enemy will say that line, before something comes down on them. They also have those eyes in the Crash games.