From the events after Mutant Pumpkins From Outer Space, mutant zombie carrots are arriving from the garden. When B.O.B. opens a gate he doesn't know a carrot is in there then he saw it after ruining the costume contest that Carl Murphy told him. But when B.O.B. put the carrot inside it bite Carl into a zombie and Wendy Murphy told everyone to run. When Dr. Cockroach got the carrot into pieces it turns into more carrots but B.O.B. kept turning them into pieces. After General W.R. Monger arrives he's bitten by the carrots and turned into zombies and B.O.B., Dr. Cockroach, and The Missing Link run inside the house. There was more carrots near the back door and Link stopped them but they push him outside and got bitten by the carrots and turned into zombie and B.O.B. and Dr. Cockroach run upstairs to Susan's room. But there is a zombie carrot on B.O.B. and he didn't got bitten because he didn't have a brain. When Dr. Cockroach told B.O.B. to eat all the carrots B.O.B. said no and got his flashback when Monger is feeding B.O.B. as a baby were eating carrots for his entire life. After saying no Link arrives and B.O.B. saw that Dr. Cockroach is turned into zombie. And then B.O.B. is eating all the carrots but there is one more carrot left but B.O.B. can't eat because he's to fat but he did eat the carrot. Then Monger, Link, & Dr. Cockroach aren't zombies anymore and are happy that B.O.B. broke the curse.
Susan herself doesn't appear in this film, but her parents do.
Bret Marnell voices the zombie carrots.
This is the Third feature in the franchise to take place in Modesto, after Monsters vs. Aliens (2009) and Monsters vs Aliens: Mutant Pumpkins from Outer Space (2009).
Released theatrically with Rio 2 (2014) in Argentina and Uruguay.