There are currently 6 mobs in the game.
Creeps[]
Creeps are mobs that will sometimes pop out from the sides of the screen in every biome except Ocean. If it is tapped on a couple times before disappearing, it will appear again on either side of the screen ,but a bit smaller. After this has occurred a few times, it will instantly break several blocks, and give you 2-4 gunpowder. It does sometimes spawn in the jungle but is very rare.
Ocelots[]
Ocelots occasionally appear from the sides of the screen in the Jungle biome instead of Creeps and drops gunpowder and grants critical chance for 15 seconds when tamed by repetitively clicking on it.
Tumbleweeds[]
Occasionally floats across the screen when there is inactivity in the Mesa biome. It gives you 4-8 Tumbleweed blocks. Also appears when you use the tumbleweed pickaxe ability.
Starfish[]
Occasionally floats across the screen when there is inactivity in the Ocean biome. It gives 4-9 Starfish Shards. It appears when you use the coral pickaxes ability.
Guardians[]
Occasionally floats across the screen in the Ocean biome. To defeat it, you must tap it multiple times and it yields 3-7 prismarine and 0-3 pearls.
Asteroids[]
Occasionally floats across the screen when there is inactivity in the moon biome. It will give 3-7 Asteroid Shards. Also appear when you use asteroid pickaxes ability