During World War II, he fought in Grampa's World War II company, the Flying Hellfish, as their Radio Operator. He is also constantly the butt of several jokes by his comrades, with one particular joke involving a note saying "shoot me" being placed on his backside. He remarks that he "didn't join the unit to make friends" grudgingly after realizing the prank. He desired three chicken dinners every day after deciding to make the tontine on the Hellfish Bonanza.
Despite not being Seymour Skinner's birth father (Skinner's birth father was a soldier heading for the Korean War[2]), Sheldon resembles him a lot both physically and mentally however since the flashback showing Sheldon is in Bart's mind it may be that the resemblance is Bart's invention.