If Grandpa Harley was dead at the beginning of the webcomic, then why does he show up during the game driving that big ship?

Temporal Shenanigans, he doesn’t just show up there in the ship- He also hunts down Underlings and Minions, which he displays in his house, and brings Dead Dream Self Jade to Earth to have her taxidermed. Either he used his ship to go through Meteor Defense Portals, or merely stepped on the Prospit/Derse Telepads on the Frog Temple, which may have linked to the time the Session was actually happening merely because of Time Shenanigans. The guy is the one who got the entire code for SBURB after all so chances are he knows the shortcuts in and out.