Tourettes Guy's Grandpa is mentioned in an interview with the Tourettes Guy dated 18th November 2004. All he says is that he died 15 years ago, and that "Nobody gave a shit!". Because of this, it is possible that he was not well liked within the family (although if he was anything like Danny and Danny's Dad, this makes sense) and it reveals he died in either 1988 or 1989 (more likely 1989).