Hannan is the creator, executive producer, and showrunner of the Nickelodeon series CatDog, for which he also wrote and sang the theme song.

[citation needed] He is the story editor, sometime songwriter, and interstitial producer of the animated PBS Kids series Let's Go Luna!.

He co-founded the company FutureVision, which produced a TV concert series featuring blues artist Muddy Waters, Albert King, Buddy Guy & Junior Wells, Bobby Bland, Otis Rush, and Blind John Davis.

[citation needed] Hannan has taught, lectured, and led art, writing, animation, and creativity workshops for pre-school through college students.

[citation needed] He has worked as a graphic designer and art director and created illustrations for magazines, newspapers, and advertising.