Tap toys are icons at the bottom of the DS screen in the Wifi Plaza, which have certain effects when you touch them. You are loaned a tap toy before you enter the plaza, and they start out as 01, the lowest grade. They can make noise or just have an on screen effect. You may ask another player in the Wifi Plaza to loan their tap toy to you (or they can ask you.) By playing plaza games you are able to upgrade your tap toy. You may only upgrade your tap toy twice, from 01 (start) to 02 and 02 to 03.
The tap toys are:
Cymbal: Crash sound
Bell: Jingle sound
Whirl: Light circles you with a sound
Popper: Pops and shots confetti in front
Ripple: Ripple of light surrounds you with a noise