In a parodying mutant land, humans Adam, Bree, and Chase discover a creature named FrankenLeo living in the basement of their father, Donald Henderson, who announces that he was turned into a vampire by a woman named Tashcula, whom he is about to marry. However, an evil witch named Giselle and her shape-shifting bat Marcus are out to get them, and they must create a Mutant Academy to keep FrankenLeo safe, as well as all the other mutants who they come across, including Mutant Chyna-a Medusa, Mutant Olive-a mad scientist, Mutant Fletcher-a vampire, Mutant Bob and Mutant Angus-both zombies- and Mutant Spin-a literal tornado. While they have fun there, Giselle and Marcus become too powerful with the Arcturion, a mysterious space rock. They almost kill Bree, who is taken by a helpful vampire-Oliver, Fletcher's brother-and his best snake-human hybrid bud, Kaz, to "Frighty Med", a mutant hospital. Her life is saved by Oliver turning her into a vampire-thus rendering her a mutant-and they defeat Giselle and Marcus. However, Doncula, as Donald now calls himself, announces that the original team of Bree, Chase, Adam, and FrankenLeo must be broken up, with two of them overseeing the Academy and two of them joining a new "Smellite MutANT Force." Oliver, Fletcher, Kaz, Olive, Angus, and Chyna are on the team, along with Oliver's girlfriend, Skylar, who is an ordinary human. There first mission as a team involves the mystery of alien Caduceo, who is revealed to be Skylar's father, Horace. Sadly, Caduceo transforms Kaz into a human and claims Skylar is a disappointment, so he transforms her into a snake-human hybrid. Happily, Caduceo is defeated, but Kaz and Skylar remain in their altered states. Two shapeshifters, Alan and Gus, invade their home one night, and turn into Kaz and Oliver, kidnapping the real ones.The episode ends on a cliffhanger.
- Jake Short as Fletcher and Oliver Quimby
- China Anne McClain as Chyna Parks
- Bradley Steven Perry as Kaz Duncan
- Sierra McCormick as Olive Doyle
- Paris Berelc as Skylar Storm
- Kelli Berglund as Bree Davenport
- William Brent as Chase Davenport
- Aedin Mincks as Angus Chestnut
- Jesslyn Wanlim as Giselle Vickers
- Mateus Ward as the voice of Marcus
- Brandon Salgado-Tellis as Mutant Bob
- Max Charles as Mutant Spin
- Devan Leos as Alan
- Augie Isaac as Gus
- Carlos Lacamera as Horace
- Hal Sparks as Donald Davenport
- Angel Parker as Tasha Davenport
- Spencer Boldman as Adam Davenport
- Jeremy Kent Jackson as Douglas Davenport
- Tyrel Jackson Williams as Leo Dooley
- Despite the title being Scary Rats with an s at the end, it seemed that FrankenLeo was the only true "scary rat" to most people, seeing as Bree did not become a vampire for quite some time.
- This episode pokes fun at the first episode of Lab Rats, the Bionic Island Arc, the crossover episode, and the series finales of both Lab Rats and Mighty Med. It also serves as a continuation of the MutANT Farm Saga of ANT Farm.
- This episode was originally is shown in two parts. Part 1 ends after Bree nearly dies, and features a funny scene between Adam, FrankenLeo, Mutant Bob, and Mutant Spin at the end, which was deleted in the 1-hour version.
- Apparently, Alan and Gus are now shape-shifters instead of Roman and Riker.
- Vampire Douglas is not in a wheelchair, and is still able to see.