While playing "Frogger: Helmet Chaos" with one of the following GBA games in the second cartrige slot you will unlock hidden costumes in the "Costumes" menu.
With "Frogger's Journey:
The Forgotten Relic" you get the "Punk Costume"
With "Frogger's Adventures 2:
The Lost Wand" you get the "Pirate Costume"
