Grandpa Jefferson

Grandpa Jefferson is Rowley's Grandfather and Robert Jefferson's father. He made a cameo appearance in Rodrick Rules in which Rowley's family celebrated his birthday and Greg was invited too.He is unhappy with the flavour of the cake and says that he wants chocolate cake for his next year's birthday but Greg says that it would only be possible if he is alive the next year, this angers Rowley's father.

He doesn't appear in the movie, his scene is replaced by Greg's own Grandfather

Trivia

 * He might be deceased as he was never ever seen again.