Aaron

From DariaWiki

Quinn mistakenly calls Zachary "Aaron" in Monster. This is the only mention of Aaron in the entire series. Clearly, Quinn knows who he is.

We do not know if there is another student named Aaron at Lawndale High, or if Quinn knows this student, or if Quinn likes him/has dated him, or what Quinn is thinking when she makes this error. Perhaps she got to the end of her list of potential dates and started over in the alphabet too soon.