Episode name reference to/pun on: The 1983 film Mr. Mom
January 21, 1998
Rob Renzetti Genndy Tartakovsky
Sister Mom is the first part of the 23rd episode of the second season in Dexter's Laboratory. In this episode, Dexter has to attend a conference with the school principal without Mom knowing. He has Dee Dee go in Mom's stead, but trouble arises when Dee Dee doesn't behave like her.
Dexter and Dee Dee are walking home from school for the day. Dexter has a note in his hand regarding a parent-principal conference. Annoyed, Dexter hatches a plan with Dee Dee to prevent Mom from finding out about the conference, by using the Molecular Makeover Machine to change Dee Dee's outer appearance into Mom's. At Huber Elementary, Dee Dee and Dexter are waiting out in the hallway for their principal to see them. During the meeting, Dee Dee starts behaving erratically and causes interruptions. The principal tells her that Dexter got an A minus on his last test. Dee Dee then yells at Dexter for something so trivial, as she expected something like stealing the school mascot, blowing up the science lab (which Dexter takes offense to) or T.P.ing the principal's office (this time offending the principal). Dexter, however, asserts that it's Dee Dee's fault he got an A minus because she keeps bothering him, but Dee Dee retorts by saying he will never be as popular as her, prompting a fight between the two. Because violence is against the rules, the principal ends the scuffle by making both Dexter and Dee Dee attend a meeting with their school counselor. During the meeting, Dexter, disguised as Dee Dee, makes her sister look like an idiot while Dee Dee, still disguised as Mom, tries to defend her intelligence. A dog, disguised as Dexter, barks and pants when asked a question. The counselor ends the meeting early. She and the principal go get lunch while Dexter and Dee Dee continue arguing.
The title card shoes Dee Dee, back to normal but dressed as her mother, reprimanding her brother for writing the episode's title on the wall. This indicates that Dee Dee can be firm to her brother if necessary, especially when he does something careless.
For plot purposes, Mom was slightly out of character in this episode, being overly complimentary to her children, praising them and giving them tons of compliments.
When Dexter activates his makeover machine he says "It's Morphin' Time!" while doing a fist in hand gesture similar to the pose that Jason and the other Rangers use when getting ready to morph. This is a reference to the morphing sequence in the original Power Rangers television series, Mighty Morphin Power Rangers as well as Power Rangers Zeo.
First on-screen appearance of the school Principal, and second appearance after a "voice only" cameo in "Dexter's Rival".
The Dog's makes an out-of-body cameo in this episode, having switched bodies with Dexter at the end. His original body was never seen, but his voice was heard and his mind was embodying Dexter at the end.
Apparently, Dexter and Dee Dee were walking home from school, without backpacks. The only thing, being taken with them was Dexter's note.
When Dexter was crying and running up the stairs, the note from school had completely disappeared. Yet, in the next shot of him entering his room, it was in his hand again.