Role in The Ugly Truth
In the middle of his first appointment with Greg, Greg accidentally bites down on his finger during some oral x-rays. As a result of his anger from his bit finger, he prescribed a headgear to Greg which he didn't need. The next day, Greg couldn't find his headgear. The headgear was later stolen by Manny Heffley, which Greg considers to be a blessing.
- Dr. Kagan's appearance is quite identical to Chirag Gupta's father. The only difference is the presence of his moustache.
- It's mentioned in the second book that Greg brushes his teeth at least four or five times, so despite his eating and drinking habits, he takes pretty good care of his teeth (for the most part at least).