The Petri Dish is a console/mobile item used to summon the Pet Slime. The Pet Slime can be distinguished from normal Blue Slime by its darker shade of blue. It can be found in underground chests and Dungeons, it can also be dropped by Shadow Slime. When used, it inflicts the 'Pet Slime' buff which causes a Blue Slime to follow the player until death or manual deactivation. The Slime will fly through blocks to reach the player if they get too far away from it. It has the same effect as the Spectre Boots when flying. The pet, despite its color, is different from the Blue Slime. The buff for the pet Slime says "He's a real slime ball".
Similar to the Collector's EditionPet Bunny, it won't take or inflict any damage and will vanish if the player dies during its effect. This item can be reused an infinite amount of times. If the player uses it while the buff is active the pet will despawn.
Sometimes when creating a new world with the pet slime buff active, the player may spawn in the new world with two slimes, one that will follow them, the other will be unresponsive and just hang in the background.