This enemy is found only in the mobile version(s) of Terraria.
The Diseaster Bunny is a Mobile Edition only monster that can only be found around Easter before defeating the Lepus boss. It has a 100% chance of dropping a Suspicious Looking Egg, which can be used to summon the Lepus. Diseaster Bunnies look like small versions of Lepus. It can sometimes spawn randomly in or near the forest. It can also be spawned by the Lepus boss itself. It also has a chance to drop the Bunny Hood, only when spawned by Lepus himself.
"Diseaster" is a portmanteau of the words disaster and Easter. It may also be a portmanteau of disease and Easter.