At the end of the Deedeemensional segment Dexter is reading the note that Deedee gave him and what he is reading is not what is written on the note.
Although "Deedeemensional/Dial M for Monkey: Magmanamus/Maternal Combat" aired on April 28, 1996 on TBS and Cartoon Network, "Dexter's Rival/Dial M for Monkey: Simion/Old Man Dexter" were actually the first produced episode made in the same year, creating a continuity error in the American broadcast.