Mouse: I just passed that part myself. I hope this is what you are talking about:
Go to the area in the upper left, where theres some stairs, and a barrel up on a raised part of land. Do the spin jump thing to go from the top of stairs to the barrel. Get luigi to jump in it from the bottom...
@Maximumbeans, Indeed. I've been working on getting this Infecutus chip to work on my PS2. But after soldering, I realised that a plastic piece was missing from the power ribbon cable to the power and eject buttons.