Seymour finds a seed from 200 million years ago and helps it grow into the plant known as Junior. The plant tries to return home but, upon finding that he cannot, stays with Seymour and helps Mr. Mushnik's flowers grow.

Seymour joins a home economics class where he and Junior conspire to make a human–plant hybrid a la Frankenstein. Meanwhile, Audrey decides she wants to be a refrigerator repairman.

A trip to the Skid Row Museum of Uninteresting History inspires Junior to travel in time to warn plants about the rise of the dinosaurs and keep his place in the food chain.

Seymour's science project, which was made by Junior, wins a science fair and attention from Seymour's favorite celebrity. However, the scientist wants to steal Seymour's project and use it for himself.

Seymour brings home a female Venus flytrap, which Junior falls in love with.

Junior persuades Seymour to buy a new pair of shoes and makes them fly.

Infuriated by the tradition of jack-o-lantern carving, Junior joins Seymour and Audrey's trick or treating to steal them back via his vegetable magnetism abilities.

A reaper shows Seymour a future where the Mushnicks own a yogurt shop, Paine is winning awards, and Seymour is a politician. Meanwhile, Junior dreams that he runs a hotel for flowers.

Seymour and Junior learn the hard way about lies when Mrs. Krelborn's low-fat ice cream disappears.

Weary of the limitations that come with having roots, Junior tries to give himself legs and inadvertently winds up sharing a body with Seymour.

Junior watches in horror as the oldest tree in the world is turned into paper and leads a revolt composed of used paper products that swamps Skid Row.

Paine's aunt starts to date Mr. Mushnik under the delusion that he is a rich dude. Dismayed from the news, the usually career-oriented Audrey expresses her desire to become a housewife.