Cookies are items in Pac-Man Party that you get from the Cookie Factory. You can get more by landing on your castle as a castle bonus.
Power cookies are cookies that give power to the user. They help the player's chances at winning a minigame. When used, the minigame playing will briefly pause, and the character who used the power cookie will dash from the right side of the screen to the left side. The player can have a maximum of eight power cookies in Party Mode, and three in Minigame Mode.