The animation focuses primarily on Twilight Sparkle and Spike. The title and overall plot is a reference to the musical Little Shop of Horrors, itself based on the similarly named Roger Corman B-movie.
Principal Celestia leaves Twilight Sparkle and Spike in charge of tending to her garden while she's on vacation. Unbeknownst to Twilight, some Equestrian magic enchants her watering can. As Twilight begins watering and singing to the plants, the plants start to grow and come to life, singing along to Twilight's song. As Twilight gives them more and more water, the singing plants become increasingly aggressive and demand more. Twilight sends an SOS text to Applejack, and when she arrives, she turns on the sprinklers to turn the plants back to normal. Just then, Celestia returns and warns Twilight not to over-water the plants.
- The short's plot is quite similar to the Little Shop of Horrors film plot. When the plants start coming to life, they start taking the place of the Audrey II, and Twilight start taking the place of Seymour Krelborn as the plants start begging Twilight to give them more water, just like when Audrey II keep begging Seymour to feed him.