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

Trivia

 * When he asks for a chocolate cake for his next birthday Greg says he could only have it if he is alive next year, hinting that he might be very old.
 * He might be deceased as he was never ever seen again.