- Age: 15...months keeping my shape.
- Parent: The Blob
- Freaky Flaw: I ooze slime wherever I walk.
- Killer Style: Anything that helps keep my form solid.
- Favorite Activity: I like playing sports because my slime usually screws up by opponents.
- Favorite Color: A gooey green.
- Favorite Food: Anything with jelly.
- Pet: Gooze is my pet slug. We leave similar trails.
- Biggest Pet Peeve: When people get stuff stuck inside me.
- Favorite School Subject: Physical Deaducation
- Least Favorite Subject: Home Ick
- BFFs: Gary Goyles
- GFs: Howleen Wolf
Slimen has been attending Monster High for a few years but really begins to branch out when he begins to control his form and attracts the attention of Howleen Wolf. Gina Djinn helps Howleen impress Slimen but each ends up failing. Slimen decides to go out with her after seeing how much trouble they went to for Howleen. They end up dating soon after. He evades capture by The Masked Lantern because his body can't be properly absorbed by his lanterns. He attends a dance with Howleen after he is defeated.
He and Howleen continue their relationship and he befriends Gary Goyles. He helps Gary realize his new life and helps him with the attention he gets from Rochelle. He and Howleen have trouble when she tries to become her sister. Slimen convinces her to be her own person and stop acting like her siblings. They help fight off Gillian's invasion.