LABretto is the second part of the 38th episode in season 2 of Dexter's Laboratory. The episode is a re-telling of how Dexter's lab came to being in the form of an opera.
The story begins with Dexter's birth and his first meeting with Dee Dee, showing that their "rivalry" has been a recurring element in their lives throughout their infancy and childhood, with Dexter building a new invention almost everyday only to have it accidentally destroyed by Dee Dee. Upon the discovery of the location that would serve as Dexter's lab, Dexter believes he has finally found a sanctuary away from his sister, but in the end she still manages to destroy his first great invention. The story then ends with Dexter confessing that his life is not a fantasy to him and it is his reality where he and his sister must remain together for the rest of their lives for better or for worse.
This episode shows Dexter getting his first pair of glasses from a doctor shortly after his birth.
When Mom is at the hospital, she has different hairstyle, however, when she and Dad come home, her hair is same as in the present.
One possible explanation for this is that she simply didn't have chance to fix her hair while in the hospital.
Dexter's First Invention as seen in this episode is notably different when compared to how it did in "Lab of the Lost". The outer wooden shape with a metal surface remains the same, but in this episode, it is a pear grabber and in "Lab of the Lost" it is an alarm.
One possible explanation for this is that the writers forgot about the device from "Lab of the Lost" or that the device seen here was not intended to be his first invention.