Mr. Hinkle is a nice and kind old man who lives right next door to Caillou. He likes having fun with Caillou and Rosie and is also good friends with Caillou's Daddy and Caillou's mommy. Caillou visits him sometimes. He is the other grandfather figure to Caillou and Rosie.
Mr. Hinkle has lived in the Caillou Neighborhood and has a 2 story red house. He has an older sister named Nancy who has a pet rabbit named Snowball. She also appeared in the episodes Farmer for the day and Mystery carrots. In the former, his first name is revealed to be Paul. Mr. Hinkle does not seem to have a wife.
At a garage sale, Mr. Hinkle serves hot dogs, but instead of serving them on buns, he serves them on slices of sandwich bread.