Gimpy got her nickname because of her uncanny ability to do anything with gimp. Her one-leggedness is a coincidence. Gimpy was a very special little girl, known all throughout all of Gimp-Land for her magical power of GIMP and her tiny, tiny brain.

That jar in her leg hole is her favorite jar of gasoline.
She mysteriously equally distributes her weight when standing and walking. She equally mysteriously walks as if she has two legs.