Dexter's Laboratory - Season 2 Episode 12 -

Dee Dee Locks and the Ness Monster—Dexter's mother forces Dexter to read to Dee Dee when she's sick, but she makes up her own story after being bored by Dexter's story (which was actually a science article). The story is completely mixed up and makes no sense. Dexter ends up catching Dee Dee's illness.