Mrs. Mackelroy was Greg's math teacher in The Ugly Truth. Greg claims that she taught kindergarten before coming to his middle school, but feels that she's not too keen on working with middle school students. Greg says that the boys in his class all have gym class right before math with Mrs. Mackelroy. The odor resulting from the boys being so sweaty from exercising in gym caused her to complain that about her classroom smelling like a "monkey house" so the principal made it mandatory for students to shower after their gym classes.
- Diary of a Wimpy Kid: The Ugly Truth (First and only appearance)