The "Quality Time" medal.

This verb lets you fuse with another player.  When you do this, both players become one character (that you name) that both players control and talk from.  You're more powerful while fused.  If a Hamtaro player and Bijou player fuse, you will become Bijaro.

You become defused when you use the Defuse verb, or when one of the player's MP runs out.  Lose 10MP from being fused to earn the Quality Time medal.