Initially known for jokes poking fun at his youthful appearance, he has since turned his attention to more general, real world, and topical subjects, with a tightly-written style [according to whom?]

[citation needed] Since 2001, Kirshen has become a frequent performer at London clubs including the Comedy Store, and has completed several university tours.

[5] In an appearance on the podcast International Waters, he vowed that "the world has seen the last of The Wilf", although when pressed, he joked, "Well, I guess we'll never know", in reference to his album of the same name.

[3] Kirshen wrote for The Jim Jefferies Show on Comedy Central,[7] for which he was nominated for a 2018 Writers Guild of America Award,[8] and for season 5 of Arrested Development.

Guests on the episodes he has co-hosted include Rainer Weiss, Andy Weir, Adam Steltzner, Jim Green, Sheyna Gifford, Chuck Nice, Bill Nye, Jay Leno, Mona Chalabi, Joe Patterson, David Kipping, and Chris McKay.