Role in Movie
Big Blue used the MARV to observe and direct the invasion throughout Slusher and detonate the bomb that would have killed Standrew, Westick, Stick JK, and Joshtick. However, he only ends up giving BigBoi a "fatal boo boo." After seeing that all his forces have been wiped out, (there's supposedly 124 total, but MARV says that they're's 90 Blues and 90 Drabs, despite there being more Blues, and there are also Limes) Big Blue exits the vehicle, only to see that the Slush Fighters have decided to gang up on him.
Role in Game
The MARV is only a decorative addition to the Slusher level, which Big Blue leans on prior to Standrew launching him.
Sometimes however, in any other level Standrew launches Big Blue, he is leaning against nothing or just posing, while in other levels, he has a different pose.