Homer and Marge's sex life is going down the tubes due to Homer's laziness and the kids bothering them. Salvation comes in the form of Grampa Simpson, who concocts a bathtub aphrodisiac that Grampa and Homer sell to the masses. Meanwhile, Bart fears that the alleged disappearance of all the adults is part of an alien invasion/government conspiracy.
- Abusive Parents: As Homer points out, Abe's been an awful father. When Homer was watching President Kennedy on television as a child and imitates him, Abe cruelly tells Homer (while rolling up a newspaper) that America was made so idiots like Homer can't be President. Then there's the entire car argument where Abe flat-out tells Homer that he was an accident and that he never should have been born. Abe does regret how he treated Homer later on.
- Bait-and-Switch Comment: After Homer stops helping Abe to sell the aphrodisiac, Abe tries to get Barney's help and later says it's not the same without Homer. Homer can drive.
- Brake Angrily: Homer does this right after Abe tells him his birth was an accident.
- Continuity Nod: Marge mentions Bart's birth being an accident as well.
- Did Not Think This Through: Planting Homer in the audience to sell the tonic fails not only because of Homer's lousy acting skills but also because Homer's face is in the tonic's label.
- Get Out: Homer kicks his father out of the car after he is told that his birth was an accident.
- Left the Background Music On: When Homer and Abe are fleeing an angry mob, Homer tells Abe that the mob only started chasing them after the music started. Homer is proven right when he turns the music off.
- O.O.C. Is Serious Business: Normally, when Homer's mad, he'll explode at you. Abe's "You were an accident!" comment evidently hurt him enough to put him in Tranquil Fury mode.Abe: If I hadn't taken that tonic 38 years ago, you would never have been born and I would be happy! You were an ACCIDENT!
Homer: (slams on the brakes and speaks very softly but still evidently enraged) Get out.
Abe: (realizes what he just said) I'm so sorry I said that...
Homer: (still softly) Out.
- Sarcasm-Blind: When Lisa jokingly suggests that the adults of Springfield have become reverse vampires who have to get home before dark, all the other kids become terrified of the idea, and instantly accept it. Much to Lisa's annoyance.
- Bart writes on the chalkboard that his homework wasn't stolen by an one-armed man.
- After years of Professor Frink as Jerry Lewis' Nutty Professor character, we see him as Buddy Love after he drinks the tonic.
- Snake Oil Salesman: Homer and Grampa's traveling show has all the hallmarks of this, including old-fashioned barking from a platform, and planting people in the audience, but the tonic really does work in this case...until the duo break up.
- The Casanova: Professor Frink becomes this as soon as he drinks the tonic, and he picks up a female scientist.
- The Conspiracy: The children of Springfield suspect something huge is going on involving "reverse vampires" because their parents rush home before nightfall. They are actually just having sex.
- Tranquil Fury: Homer when Abe calls him an accident. It scares Abe into apologizing, to no avail.
- Weekend Inventor: Grampa Simpson managed to come up with a fast acting aphrodisiac out of random things he had lying around (that was originally supposed to be a cheap substitute for holy water), similar to how Homer came up with the flaming Homer.
- What Happened to the Mouse?: The kids spying on their parents disappears eventually. A deleted scene had Ralph telling them that the parents aren't around because they're busy having sex. The writers edited this out because they didn't think Ralph would be smart enough to understand that.
- You Can't Go Home Again: Homer and Grampa go back to their old farm, and recollect happier times (and unhappy times), but it's worn down and just not the same. Then they accidentally burn it down.
- You Were An Accident