This was only the second cartoon series to premiere on prime time network television in the United States. The first was another Hanna-Barbera production. "The Flintstones" (1960).
In the opening title song "Top Cat" (seen in every episode) the waiter should be shown in front of the lunch box on the table. His torso is behind the box until Top Cat jumps up and runs for the taxi. At that point the waiter "pops" fully in front of the lunch box. This was related by Arnold Stang on the DVD commentary and he was very annoyed (even years later!) that the studio would let such an error occur every week.
Professor Zimbach:
[admiring a contemporary painting]
This man has artistic temperament, like Van Gogh. You know, the painter who cut off his ear and sent it to his girlfriend.
Top Cat: Oh, yeah, to ask her why he hadn't heard from her.