"Jimmy Jest: His Shadow's a Pest" was a strip that ran in Cracker from issues 38 to 87. Drawn by Ken Harrison, it starred a boy with a living shadow that played pranks.
The first strip provided an origin story. Having emptied his water pistol, Jimmy refills it from a jar of chemicals perched on a laboratory windowsill. He then playfully squirts his own shadow with the mysterious liquid, causing it to come to life and punch him in the face.