Brian Posehn is an American stand-up comedian, actor, voice actor, musician, and writer. After numerous appearances as a television guest star, Posehn acquired his first major recurring role in HBO's Mr. Show with Bob and David (1995–1998). He is known for his roles as Jim Kuback on The WB's Mission Hill and Brian Spukowski on Comedy Central's The Sarah Silverman Program. Posehn had a recurring role on The Big Bang Theory as geologist Bert Kibbler.