I picked up my copy of Alex Robinson's Box Office Poison at my very first Comic Con, back in 2001, but I didn't read it until I got home. And it was on the flight home that Gene and I started brainstorming the comic strip that was to become Unshelved. So the fact that one of the main characters works in an establishment where people ask lots of dumb questions about books, well, that's a coincidence.
But we did steal, wholesale, the concept of a "question time" where several characters answer the same question. I immediately wrote Alex and fessed up, and he graciously admitted that he had in fact stolen the concept from yet another cartoonist. And so the circle of plagiarism continues, expanding ever outward.