Go to the Carrot Juice level in the Formerly A Prince
chapter. When you get to that level, go halfway through until
you get to the first hidden Giant Red Gem. Smash it by shooting
it with any gun, then go all the way to the right, where the bouncy
thing is located. Do not go on it, or you will go up through the
rocks and have to do it again. Keep going right until you hit
the wall, then run all the way to the left, where you first dropped
down to get to the Giant Red Gem. It will be there again, and
you can shoot it to get more gems. Go all the way to the right,
then all the way to the left again. It should appear again. Repeat
this to get as many gems as needed.