Pause the game and type cheatercheaterwimpwimp and you will instantly go up to
45 credits. Do it again and you will get 99 credits.
WARNING: This will have a side effect that makes it hard to get awards 

Type toast whenever you see a trailer and it will turn into a toaster 

Type wolfdog when ever you see a rabbit and after a few seconds it will chase its tail
and then disappear. 

Type bacon whenever you see a pig and it will turn into a balloon and fly away
(unless it pops first). 

Type in USPA87419 to summon the parachute kid.