Do the following to get these unlockables:
Character mini-games: get 30 points or more for a character. Touch Orbulan's UFO to make the mini-game appear.
Bonus mini-games: beat the high score on all mini-games that have high scores.
Credits: win Wario Man's micro-games.
Monster Megamix: win Wario Man's micro-games and wait for the credits. Touch the pink "teddy bear" that leaves the taxi.
Hardcore Mix: get 25 or more points in Monster Megamix. Touch the white "teddy bear" that leaves the taxi.
Gnarly Mix: get 15 or more points in Hardcore Mix.
Silver character crown: unlock all micro-games for a character.
Gold character crown: pass all micro-games for a character.
Whistle A Tune toy: get Gold crowns for every character.
Air Dude souvenir: score 20 or more points in Gnarly Mix.
Party Tooter souvenir: glide more than 100 yards in the Air Dude souvenir.