A plan to get Roger's home back goes horribly wrong, and the penguins must stop one of their own from going on a rampage.
The penguins are testing out their habitat's new defense grid when Roger the alligator bypasses all of it by coming through the sewer entrance (which he calls the front door). He has come to them for help because the sewer rats are stealing his stuff and are taking everything in his home. After attempting to train Roger, the penguins find he loathes violence of any kind, and Skipper decides it would be simpler to switch his gentle mind with Rico's world-class-psychopathic mind. Kowalski promptly makes a device that allows them to switch those minds.
Rico's mind, now in Roger's body, goes to Roger's home without even being ordered, and beats up the rats. Unfortunately he doesn't stop there, and Kowalski realizes that Rico and Roger's bodies differentiate in warm- and cold-blooded temperatures, making Rico even more psychopathic than usual. This, along with Roger's body, has him go on a rampage through the sewer that carries into the city. Roger, trapped in Rico's body, wants to help out but when he keeps burping up weapons involuntarily, Skipper tells him he isn't cut out for this type of action.
The penguins try to tie Rico up but he is too strong. Roger helps out by singing Rico to sleep. Rico falls asleep and the penguins are able to switch their brains back and return everyone to normal.