Portia's mother Susannah (played by Lily Tomlin), has an art piece on her wall showing a fish riding a bike. This is in reference to Irina Dunn's quote "A woman needs a man like a fish needs a bicycle", later popularized by Gloria Steinem. This is thrown in to show Susannah's feminist views. She also quotes Erica Jong at one point.
The Latin inscription at Quest, "ipsa scientia potestas est", translates to "knowledge (itself) is power".
Both Paul Rudd and Wallace Shawn were in Clueless.