Cool Cat cameos: Sylvester draws him on the chalkboard in "Blackboard Jumble" at 8:38; he appears when Sylvester turns on the light in "What's the Frequency, Kitty" at 13:48.
"What's the Frequency, Kitty?" is a reference to a real life incident where news anchor Dan Rather was attacked by an unknown man (later theorized to be William Tager) who repeatedly asked Rather, "Kenneth, what is the frequency?" as he beat him. The attacker was convinced that TV networks were beaming signals into his brain and demanded to know the frequency so he could block them. The incident inspired a song by R.E.M. called "What's the Frequency, Kenneth?".