The show opens at the Petropolis Museum of Natural History, where a tour guide (Kitty in disguise) is teaching visitors at the museum about the museum's prized possession the Kruger Rat, which has the ability to control the minds of rats when exposed to the light of a full moon. Just as she finishes, Verminious Snaptrap bursts in through the skylight, and after a somewhat embarrassing introduction of himself (he gets confused with two other villains, and finds out that nobody in the museum knows who he is, then he explains to them), and manages to steal the Kruger Rat. The tour guide sheds her disguise, revealing herself as Kitty Katswell and goes after Snaptrap. Meanwhile, on the other side of town, Dudley is playing with his new chew toy (accidentally injuring his mother in the process), which lands in the back of the D.O.O.M. truck, and Dudley gives chase to it, harming Kitty in the process. Once inside their headquarters, Snaptrap announces his plans for the Kruger Rat and how he'll use his fellow rodents to commit crimes around the city... then Dudley bursts in, completely oblivious as to what's happening, still after his toy, and injures Bad Dog, Francisco, and Leather Teddy while trying to get it. Snaptrap assumes that Dudley's come to get the Kruger Rat, only to find out that Dudley just wanted his toy back. They both laugh this off, and Snaptrap uses this to escape, while all Dudley can do is just say "Wow, what a weird and creepy dude." As soon as this happens, Kitty, along with several T.U.F.F. Agents, and the Chief, arrive. Kitty is intent on arresting Dudley for "interfering with her operation", but the Chief is more concerned as to how Dudley managed to tackle three of the city's most wanted criminals.
Back at T.U.F.F. HQ, Dudley is subjected to various tests, and it's discovered that he has the abilities of every breed of dog there is (and a dash of billy goat, which Keswick can't quite explain). After seeing Dudley injure at least five T.U.F.F. scientists, the Chief instantly decides to make him a T.U.F.F. Agent, with Kitty as his trainer. Despite Kitty's protests (and a brief fight scene/slap fight with Dudley), the Chief puts them back on the case. Heading to the pier where Snaptrap's escape pod landed, the two begin to search... well, Kitty actually searches as Dudley just talks about how awesome having a cape would be. They fall into one of Snaptrap's traps, and are later tied up, with cheese on their heads. Snaptrap proceeds with his plan, and uses Dudley and Kitty as an appetizer for his rat army. Kitty tells Dudley to use his super sense of smell to tell her where the rats are coming from, and they gain an advantage over the rats. Dudley backflips into the air, resulting in his cheese mask slipping off. He rolls around in it, causing the cheese to seep into the ropes and the rats to unwittingly gnaw them off. Once free, Kitty and Dudley proceed to beat up the rats. Snaptrap boasts that he still has the Kruger Rat and will still go through with this plan. However, he ends up falling into a cage beneath him thanks to Dudley pressing a release button for the catwalk to collapse under his feet.
The following day, the Kruger Rat is returned to the museum and Dudley gets a new suit with a cape. He then decides that he wants to press a button in the T.U.F.F. Mobile, despite Kitty's warnings. Dudley presses it anyway and is ejected out of his chair. Kitty says that maybe working with Dudley might not be so bad after all... and gets hurt when Dudley crashes onto her and the T.U.F.F. Mobile.