Simpsons Season 6, Episode 10: Grampa vs. Sexual Inadequacy

Homer and Marge's marriage is beginning to sour due to their fading sex lives. Grampa concocts a tonic that successfully cures their problems. The effectiveness of the tonic results in he and Homer going into business together, selling "Simpson and Son's Tonic" to the public. When they visit the farmhouse where Homer grew up, the two get into an argument, resulting in Grampa calling Homer an "accident".