Scenes of "Science Fiction Parody" are later featured in "And Justice for None" as a flashback sequence. However, it is an unsaid rule that if cartoon character(s) are to appear after being destroyed in an episode, that they are not to remember any happening of the one in which they were destroyed. In the case of "Science Fiction Parody," the Earth exploded - therefore everyone was destroyed (other than the Narrator). Therefore, none of them should be aware of the happenings of that episode. And for the record, this rule does not apply to video game characters, especially villains.