In the South Park episode "You're Getting Old" which follows "Ass Burgers", Stan celebrates which birthday?
Ass Burgers: "Ass Burgers" is the eighth episode of "South Park"' s fifteenth season and the 217th episode of the series overall. Ass Burgers:  The episode picks up where the previous episode, "You're Getting Old", left off. You're Getting Old: "You're Getting Old" is the seventh episode and the mid-season finale of the fifteenth season of the American animated television series "South Park", and the 216th episode of the series overall. You're Getting Old:  In the episode, Stan begins to develop a profound sense of cynicism after celebrating his tenth birthday, where he is literally seeing everything as "crap".
tenth birthday