The Ewecus has a 50% chance to spawn at the end of a series of Suspicious Dirt Piles instead of a Varg. It utilizes the same increased chance of spawning as a Varg does, starting off at a relatively low 5% on Day 1 and gradually increasing to 33% by Day 100 (both of these values will be halved for finding either the Ewecus or Varg specifically). This makes hunting for the Koalefant alone more risky due to the nature of its attacks, encouraging players to work together.
The Ewecus has a short-ranged melee attack and a long-ranged projectile. When it uses its short-ranged attack, it will attempt to kite the player. The projectile attack, in which it spits mucus at the player, will halt the player's movement on impact, similar to being frozen solid in Reign of Giants. The player will escape over time, but the player can escape faster with the help of other players or befriended Pigs, which will free the stuck player immediately.
- The name "Ewecus" is a portmanteau of the words "Ewe" (a female sheep) and "Mucus".
- If the player manages to herd a Ewecus in a pen consisting of second tier Walls, the player can keep it as a pet without danger, since the Walls intercept its projectile attacks.
- Wickerbottom's description of the Ewecus (Ovis chalybs) is Latin for "steel sheep", a reference to the steel wool it drops upon death.
- It is possible the Ewecus is ill, which explains its weaponized snot and disgusting looks. Wendy's quote on Ewecus and Phlegm support this, as well as the "Stuck In The Middle With Ewe" poster.
- From the game's files, there are few unused files for the Ewecus' body with most of its wool shaved off, originally meant to be shaved with a Razor for Steel Wool, similar to the Beefalo.