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.
* AbusiveParents: 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. [[JerkassRealization Abe does regret how he treated Homer later on]].
* BaitAndSwitchComment: 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.
* BrakeAngrily: Homer does this right after Abe tells him his birth was an accident.
* ContinuityNod: Marge mentions [[Recap/TheSimpsonsS3E12IMarriedMarge Bart's birth being an accident]] as well.
* DidNotThinkThisThrough: 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.
* GetOut: Homer kicks his father out of the car after he is told that his birth was an accident.
* LeftTheBackgroundMusicOn: 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.
* SarcasmBlind: 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 [[Series/TheFugitive 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.
* SnakeOilSalesman: 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.
* TheCasanova: Professor Frink becomes this as soon as he drinks the tonic, and he picks up a female scientist.
* TheConspiracy: 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.
* TranquilFury: Homer when Abe calls him an accident. It [[OOCIsSeriousBusiness scares Abe]] into apologizing, to no avail.
* WeekendInventor: 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 [[Recap/TheSimpsonsS3E10FlamingMoes Homer came up with the flaming Homer]].
* WhatHappenedToTheMouse: 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.
* YouCantGoHomeAgain: 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. [[FromBadToWorse Then they accidentally burn it down]].
* [[YouShouldHaveDiedInstead You Were An Accident]]