|Episode name pun on: Substitute Teacher|
"The Boys are Back in Town"
All the children at Pokey Oaks Kindergarten love Ms. Keane, their teacher. But one day, Ms. Keane falls ill. A substitute teacher, a green-skinned humanoid monster named Mr. Green, is called to replace her for the day. Though he may look rather sinister and monstrous, he is proven to be a nice monster who loves children and enjoys teaching them. However, when he first arrives, the Powerpuffs are paranoid about him, and come to the conclusion that Mr. Green ate Ms. Keane. Many attempts to "foil" his "evil ways" fail, and their behavior only gets them time-outs. While sitting inside as the other children are playing, the girls believe that they hear the other children screaming in fear. Taking action, the girls fly into space, performing a spinning attack, fusing into a blazing orb of energy. Luckily, the other kids catch them and successfully stop the girls from striking Mr. Green with their attack by crying out that he is a good guy. After sheepishly landing, the girls receive a stern lesson from him, agreeing that it's wrong to judge people by their looks. Mr. Green hugs the girls, and they smile, finally trusting him.
- The K.E.A.N.E. song is a spoof of SpongeBob's F.U.N. song.
- There is an abnormal amount of kids marching into Ms. Keane's class.
- Interestingly enough, Mr. Green's horns bent down as he looked up at the girls in their near-successful attack; almost like a scared animal.
- At the beginning of the episode, Mr. Green's eye is bright red instead of black.
- This is the first of a few times in Season Five that the girls are in their secondary endshot pose: Blossom standing upright, Bubbles and Buttercup bowing at the waist, turning their attention to the viewers.
- After believing that Mr. Green ate Ms. Keane, Buttercup shouts and calls him "Doctor Lecter," most likely referencing the infamous cannibalistic psychopath "Dr. Hannibal Lecter" from Silence of the Lambs.
- This is one of the most graphic episodes of the series (due to the manga-like still images shown in the Girls' paranoid fantasies).
- Moral of the story: Don't judge a person by their looks.