Dennis Tracton is a boy who is lactose intolerant. He appeared in The Meltdown. At the beginning of the International Showcase project, Dennis and several other students, including Greg Heffley (who chose it due to his fondness of pizza), opted to do a project on Italy. Due to its popularity, the teacher does a random drawing to decide who gets the country and chooses Dennis, which Greg complains is unfair due to his lactose intolerance and the fact that he can't eat cheese.
- Diary of a Wimpy Kid: The Meltdown (First and only appearance)