Biggle Tiggles

The "Teletubby" Demon was a supporting antagonist in the X-Files episode, Familiar, appearing only once - it was likely another guise of the more infamous Mister Chuckle Teeth but due to the supernatural nature of the episode and the themes of witchcraft and curses gone wrong it could easily of been its own entity, regardless of which scenario was true it would follow Mister Chuckle Teeth's agenda of child abduction and murder.