Gerald Raymond "Gerry" Rosenthal (born September 2, 1980) is an American actor, voice actor, singer-songwriter, and musician who started out acting in TV commercials at the age of 7.
 He has starred on films and short films and has guest starred in television series such as "Law & Order" and "Celebrity Deathmatch".
 He is perhaps best known for providing the voice for Jimmy Hopkins the main playable character in the 2006 video game "Bully" for which he was nominated for a 2006 Spike VGA award for best performance by a human male.
 He lives in Jersey City, New Jersey and now mostly works as a guitarist, bassist, keyboardist, and singer-songwriter.
 He teaches private music lessons and performs in gigs professionally.
 He plays bass in both a Beatles cover band called Hey Bulldog, as well as the Mama Doni Band, and guitar in a wedding band called The Jersey Joint.
 Gerry also writes, records, and plays guitar with his own original band, Big Wake.
 He freelances with as many different projects as possible, and performs solo and duo acoustic sets all over the area.
Johari Johnson is an American actress, director, comedian, screenwriter and producer.
 She has guest starred in a number of notable television series including "Moesha", "The Steve Harvey Show", "Smart Guy", "In the House", "Eve", "Cory in the House", "Mr. Show with Bob and David" and among other series.
 She has also guest starred numerous times on "The Fresh Prince of Bel-Air" and the Disney Channel Original Series "That's So Raven", each time playing a different character on both series.
Martin T. Sherman (born November 28, 1966) is an American actor, voice actor, voice director, writer and director.
 He has starred in several films and television as well as providing voice acting for several video games, one of his most recalled roles being Pac-Man in "Pac-Man World 3", the first time the character ever had a voice actor in his games.
 From 2009 to 2015, Sherman voiced Thomas and Percy and from 2013 to 2015 he voiced Diesel in the US version of the television series "Thomas & Friends".
Ernie Grunwald (born in Thornhill, Ontario, Canada) is a Canadian-born actor who has had made guest appearances in a number of notable television series.
 He has also had recurring roles on, "One on One", "The Suite Life of Zack & Cody" (as Mr. Forgess, Series 2 Episode 22), and "Two of a Kind" opposite Mary-Kate and Ashley Olsen.
 He has also guest starred on, "Friends", "My Name Is Earl", "NYPD Blue", "Reno 911!
", "ANT Farm", "Walker, Texas Ranger", "Supernatural", "Grey's Anatomy", "Bones", "The Mentalist" and many other series.
 He has also had roles in the feature films, "Cellular", "It Takes Two", "Men in Black II", and "Stealing Harvard".
 He guest starred as a restaurant manager in "Monk" ("Mr. Monk's 100th Case") and as a bumbling government official in "Psych" ("Death is In the Air").
 He also made a cameo appearance in the 1992 Disney film "The Mighty Ducks" as a fan.
"Idiots Are People Two!"
 is the second episode of the sixth season of the American television comedy series "30 Rock", and the 105th overall episode of the series.
 It was directed by Beth McCarthy-Miller, and written by co-show runner and executive producer Robert Carlock.
 The episode originally aired on the National Broadcasting Company (NBC) network in the United States on January 19, 2012.
 Guest stars in this episode include James Marsden, Kelsey Grammer, and Denise Richards.
Michael Søren Madsen (born September 25, 1958) is an American actor, producer, director, writer, poet and photographer.
 He has starred in over 200 films, including "Thelma & Louise", "Reservoir Dogs", "Wyatt Earp", "Free Willy", "Species", "Donnie Brasco", "Sin City", "Kill Bill", "The Hateful Eight" and many direct-to-video films.
 He has also guest starred in numerous television series and has done voice work in several video games.
 Madsen is known for making many films with Quentin Tarantino.
Allen Kelsey Grammer (born February 21, 1955) is an American actor, voice actor, comedian, producer, director, writer, singer, and activist.
Dominick DeLuise (August 1, 1933 – May 4, 2009) was an American actor, voice actor, comedian, director, producer, chef and author.
 He was the husband of actress Carol Arthur and the father of actor, director, pianist, and writer Peter DeLuise, actor David DeLuise, and actor Michael DeLuise.
 He starred in a number of movies directed by Mel Brooks, in a series of films with career-long best friend Burt Reynolds, and as a voice actor in various animated films by Don Bluth.
Cutter Garcia (born May 9, 1975) is an American actor, voice actor, and writer.
 He has guest starred in numerous television series, and is perhaps most notable for voicing Torn in the Jak and Daxter video game series.
Michael Henry (born March 25, 1964) is an American actor, voice actor, writer, producer, comedian, and singer, best known for his work on "Family Guy", where he is a writer, producer, and voice actor.
 He provides the voices for many characters including Cleveland Brown, Herbert, Bruce, and Consuela.
 Starting with the series' 5th season, Henry had received billing as a main cast member.
 In 2009, Henry, Richard Appel, and Seth MacFarlane created a spin-off of "Family Guy" called "The Cleveland Show", to focus on Cleveland and his new family, which aired on FOX until the show's final new episode (due to cancellation) on May 19th, 2013.
 Reruns of the show later aired on Cartoon Network's Adult Swim.

Question: What American actor, voice actor, comedian, producer, director, writer, singer, and activist guest starred in Idiots Are People Two!?
Answer: Kelsey Grammer