Rich decided to help Jeff anyway and invited him into the apartment. When Jeff smelled the enticing aroma wafting in from the kitchen, Rich revealed that he was baking muffin tops.
Not just muffins. Muffin tops.
It's a knee-jerk reaction to think of that 'Seinfeld' episode called "The Muffin Tops", in which Elaine's former boss Mr. Lippmann opened a muffin tops only shop. But Iit doesn't serve as a link between 'Community' and 'Seinfeld'. Muffin tops have always been more popular than the muffin stumps, and it would be somebody like Dr. Rich who would go to the trouble of baking only the popular tops.
Top of the muffin to you!