Beat all 25 in Puzzle mode Normal dificulty, unlocking Hard dificulty.
Beat all 25 in Puzzle mode Hard dificulty, unlocking Special dificulty.
Beat #1-24 of 25 in Puzzle mode Special dificulty.
Beat A1-E1, A2-E2, A3, C3-E3, A4-C4, and E4 in Stage Challenge
...and all this in a game I've never even played before now... :P
Oh, and don't tell me the solutions to the one I don't have, I'll figure it out myself even if I have to brute-force it...
I think maybe I'll play Frogger 2 for a while sometime later... Either that or Crazy Taxi 2... (Is it just me, or are the original combos somehow harder to pull off in the sequel??)