Question: Which commercial and stage actor trained at the improvisational comedy enterprise, best known as the first ever on-going improvisational theater troupe based in Chicago?

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The Oxford Imps: The Oxford Imps are an improvisational comedy troupe based in Oxford, England, where they perform every Monday during University term time at The Wheatsheaf pub.  They also perform annually at the Edinburgh Fringe Festival at the Gilded Balloon.

The Bent Theatre: The Bent Theatre, formerly known as Whole World Theater Charlottesville, is an improvisational comedy troupe based in Charlottesville, Virginia.  It was founded by Jenn Horne, (formerly of The Whole World Theatre in Atlanta, Georgia) in 2004.  The group began with weekly classes, then accumulated enough actors to perform monthly shows at various venues on Charlottesville's Downtown Mall.  As of 2010, its home base is Play On Theater.

Melina Paez: Melina Paez is a Los Angeles-based film, commercial and stage actor.  She has trained for improvisation at Chicago's The Second City, performed in several sketch comedy shows, plays and in non-commercial radio (DJ Slothgirl, 89.1fm WIDR, Kalamazoo).  She played Jane Doe in the 2003 feature film "Muhammad and Jane" directed by Usama Alshaibi and played Sabine in the 2007 feature film "Orchard Vale" directed by Tim Kinsella—both of which have been featured at the Chicago Underground Film Festival.  In 2011, she appears as an interviewee in TV on the Radio's film, "Nine Types of Light", directed by Tunde Adebimpe.  Melina has written about her experience of being on a bombed plane, TWA Flight 840, in 1986.

The Second City: The Second City is an improvisational comedy enterprise, best known as the first ever on-going improvisational theater troupe based in Chicago.  It also has programs that run out of Toronto and Los Angeles.  The Second City Theatre opened on December 16, 1959, and has since become one of the most influential and prolific comedy theatres in the world.

On Thin Ice: On Thin Ice, (OTI) is a Harvard College Improvisational comedy group.  OTI specializes in short-form improvisational theater taking the form of various comedy games in the style of Whose Line Is It Anyway? .

Ad-Libs: Ad-Libs is an improvisational comedy troupe based in Dallas, Texas.  Combining improvisation along with video segments, Ad-Libs was conceived by Phil Larsson in 1986.  Ad-Libs performs weekly shows at its 200 seat downtown Dallas cabaret style theater (Ad-Libs Improvisational Comedy Theater) and tours across the country for corporate events and performing arts centers.

Tracy Newman: Tracy Ann Newman is an American television producer, writer and musician.  Newman is a founding member of the improvisational theater troupe The Groundlings (as is her sister, Laraine Newman).  She was co-creator and executive producer of the 2001-09 sitcom "According to Jim".  She is also a singer-songwriter, as well as an original member of The New Christy Minstrels and lead singer of Tracy Newman and The Reinforcements.  She is the mother of artist/writer Charlotte Dean, with whom she co-directs the live comedy show "Charlotte's Shorts".

Antoine Vézina: Antoine Vézina is a Québécois actor.  A 2000 alum of the Université du Québec à Montréal with a bachelor's degree in theater, Vézina has a strong improvisational theater background, having performed in the Quebec improvisational leagues the Ligue universitaire d'improvisation (LUI, league of Université Laval), the Ligue d'improvisation centrale de l'UQAM (LicUQAM, league of the Université du Québec à Montréal), the Cravates, the Ligue d'improvisation Globale, the Limonade, the Ligue d'improvisation montréalaise (LIM) and the reputed Ligue nationale d'improvisation (LNI).  He is also a member of the improvisational troupe Cinplass.

The Immediate Gratification Players: The Immediate Gratification Players (IGP) are a collegiate improvisational comedy troupe based out of Harvard College.  They specialize in long form, free-form improvisation and are recognized as one of the top college troupes in the nation.

The Groundlings: The Groundlings are an improvisational and sketch comedy troupe and school based in Los Angeles, California.  The troupe was formed by Gary Austin in 1974 and uses an improv format influenced by Viola Spolin, learning her improvisational theater techniques from the Second City's Del Close, to produce sketches and improvised scenes.  Its name is taken from Shakespeare's "Hamlet", Act III, Scene II: "...to split the ears of the groundlings, who

Supporting paragraphs: Melina Paez The Second City
Answer: Melina Paez