Who is Pell-Mell (Pelly) from The Blue Girl and what is their importance?

Pell-Mell is Imogene's childhood imaginary friend. He is a fairly diminutive creature with elongated limbs and fingers, described as looking a bit like a skinny hedgehog with floppy ears and large eyes. He and Imogene told each other stories and had adventures when Imogene lived in hippy communes as a child.