In a scene where Romans in the Colisseum were giving a thumbs down sign after a poor performance, two of the Romans resemble Gene Siskel and Roger Ebert, drawn in the style of legendary caricaturist Mort Drucker (both gave it a thumbs down).
A minor Looney Tunes character called Pussyfoot has a cameo here. You can see her as the little black and white kitten chasing after the man with Michigan J. Frog in the Colosseum.