S2·E21 How Many Candles?

This episode begins with the children coming home from school to find Nanny in bed with the ""dreaded lergys"". The children are preparing to attend Francine's costume party. When Butch goes into Nanny's trunk to get out some make-up he sees a passport with Nanny's photo giving he date of birth as April 18, 1864, making her 106 years old. Since the 18th is the following day the children prepare to throw her party. The professor keeps trying to get Nanny to reveal her real age. She mentions how she is the image of her great-aunt who lived to a very advanced age. Just as the Professor thinks he has solved the passport riddle Nanny mentions her great-aunt's was a Libra (October).