Right, first of all: **** YEAH I FINALLY GOT PAST MOJO KING BEE ON MASTER PLAY MWAHAHAHA YEAAAAAAAAAAAAAAAAAAAAH!
Secondly; anyone else a fan?
My personal favourite PS2 game, a quirky yet fun as hell rhythm game from the creators of the also amazing Ouendan/Elite Beat Agents, boasting a strange (and sometimes annoying) cast of characters and a brilliant soundtrack. Not to mention an insanely difficult hidden difficulty that haunts me to this day!
The PSP version is one of the main reasons that would tempt me into buying a '2000. Unless you hate rhythm games (and even then this might turn you around), I can't recommend tracking down a copy enough.
The gameplay's a little tricky to explain, so here's some footage of my favourite level: