He graduated from Naperville Central High School, where a classmate gave him the nickname "Groover" which over time changed to "Gruber" and inspired his professional name.

Allen is a member of comedy group 2 Headed Dog with comedians Jim Turner, Mark Fite, and Craig Anton.

Allen has guest starred on Gilmore Girls, where he played a town troubadour, organic farmer, and a de facto minister officiating a wedding.

Allen has provided multiple voice performances, such as on animated series King of the Hill episodes "Unfortunate Son", "Phish and Wildlife", "Raise the Steaks", and "Bill's House".

Later on, Allen also played several different characters in NBC's Newsradio, and appeared as night school teacher "Randy", teaching basic auto repair and maintenance in the episode "Motor Skills" of the eighth season of the sitcom Frasier.

In 2012, Allen played the salesman of a futuristic elder care center in "Life Begins at Rewirement," an episode of the ITVS/PBS sci-fi series Futurestates.