Blake Gibbons is the Lyle in The Summer of George (Season 8 Episode 22).
Bob Balaban is Russell Dalrymple in 5 episodes. First: The Pitch (Season 4 Episode 3).
Bob Odenkirk is Ben, Elaine's boyfriend in The Abstinence (Season 8 Episode 9).
Bobbi Jo Lathan is Patti in 
Brad Garrett is Tony Abado in The Bottle Deposit (Season 7 Episodes 21-22).
Brenda Strong is Sue Ellen Mischke in four episodes. Her first appearance was in The Caddy (Season 7 Episode 12).
Brian Doyle-Murray is Mel Sanger in The Bubble Boy (Season 4 Episode 7).
Bruce Davison is Wyck Thayer, chairman of the Susan Biddle Ross Foundation in 3 episodes. First: The Foundation (Season 8 Episode 1).
Bruce Jarchow is the Doctor in The Pilot (Season 4 Episodes 23 and 24) and Mooney in The Millenium (Season 8 Episode 20).
Bruce Kirschbaum is Guy in Police Lineup in The Beard (Season 6 Episode 16).
Bruce Mahler is rabbi Glickman (AKA rabbi Kirshbaum). He appears in 3 episodes: The Postponement (Season 7 Episode 2), The Serenity Now (Season 9 Episode 3) and The Finale (Season 9 Episode 24).
Bryan Cranston is Tim Whatley, the dentist who converted to judaism just for the jokes. He is in 5 episodes. The first: The Mom & Pop Store (Season 6 Episode 8)