It's a special occasion at Castle Frank N. Stein as Chuck D. Head and Head celebrate their fifth birthday. Igor complains, but Professor Frank N. Stein remembers back to the day when Chuck was created. The lucky lightning storm had struck and Chuck was born, while Frank had also introduced Igor to Head, the skull with the rest of Chuck's brain. The scene has been rosy until scaffolding collapsed, seemingly knocking Chuck's head off. As Igor makes do with Head, putting him on Chuck's shoulders, Chuck erupts from the bandages, furious.
Five years later, Chuck still hates Igor as much as he did on the day he met him. Frank breaks up any potential fights by presenting Chuck with a birthday cake, encouraging Chuck to blow out the candles and make a wish. As Chuck wishes for a rusty spike to kill Igor with, Igor sneaks off, happy that he learned how to make bombs so that he could plant one in the cake. However, he seems to have second thoughts, not wanting to ruin Chuck's birthday, so rushes in to stop Chuck. Frank, however, interprets this as another attempt to spoil Chuck's big day and orders Igor out of the room. Amazed that he can't even be nice to Chuck if he tries, Igor walks away as an explosion occurs behind him...
- Chuck and Head aren't really five years old yet. Since they were created in Issue 10 (120 issues previously), their birthday shouldn't have been until the 2nd October. However, timing in comics is obviously different, since most 6-part stories don't take place over 10 weeks.
- The story was actually included to commemorate STC's 5th birthday and was the only non-Sonic strip alongside Showdown.
- Most of Birthday is taken up with retelling the first part of "Starring Chuck D. Head!" for new Boomers - in these pre-Internet days and without back issues available, this was the only way for them to know about it. Certain elements were altered or dropped for reasons of space, such as Igor not fighting Kevin the Bat's friends.
- Two of the panels were identical, word-for-word, with the original story, although Frank no longer called Igor a "dumkopf".
- The birthday cake resembled the one made in Boris & the Book.