Squirrel Girl x Beast Boy + Story

Critter's Origins by MoonKnightFan101:
Doreen Logan was the adoptive child of two mothers. She suffered a genetic modification which gave her green skin, a prehensile squirrel tail and the ability to shapeshift into small woodland creatures. When her parents consulted with a doctor, it was determined that Doreen wasn't a mutant even though she believed so for a long time. When she was ten years old, Doreen discovered she could communicate with the small woodland critters and transform into them after overhearing one of these rodents in her window. She subsequently saved a squirrel from being chased by a dog, and they became friends. The squirrel, who identified himself as Monkey Joe encouraged Doreen to use her abilities to help people. Ever since then, Doreen began to fantasize about becoming a superhero, and came up with the alias of the "Unbeatable Critter." Her dreams were realized when she joined The Great Lakes Patrol(Doom Patrol + Great Lakes Avengers) and later joined the X-Titans (Titans + X-Men).

Both characters belong to Marvel and DC respectively.