LOL WHY DOES WARWICK WALK LIKE THAT?

Cause he da Man!!

I think maybe he pulled a muscle wrestling with John. And he was walking with a heavy bag on one side. Also he was quite sleep deprived and probably high on adrenaline.

good *beep* question

His walk and whole demeanor/mannerisms reminded me of Roger from American Dad.

The answers here miss the fact that he walked like a penguin from the very beginning. John, on the other hand, walked with a limp. It was a different thing. Yes, just one of the extra-weirdnesses of this awful movie.