Esten made one more appearance in the UK edition in 1994 before moving back to the USA and playing the role of Luke in Party of Five. Although in demand as a jobbing actor on stage and screen thereafter, it was his 1999 return to Whose Line Is It Anyway? — in the show's new-look American format, with Drew Carey as host — which established him with a mainstream American audience. He became a regular "fourth contestant" on the show and continues to be adept at the singing games in particular, though has satisfied his early potential to become an outstanding all-round improviser.
He is currently a member of the touring Improv All-Stars group.
Esten also starred in a public service video, "Riding Straight", produced for the Motorcycle Safety Foundation's curriculum, "Motorcycle Rider Course: Riding and Street Skills" (MRC:RSS). Esten portrayed a surfer dude, a snuff-dipping hick, and a concerned friend in a bar. Esten's performance, in turns over-the-top comedy and sincere public service message, greatly invigorated the drug- and alcohol-awareness portion of the MRC:RSS. The video, part of a curriculum update for a younger "MTV generation" audience, replaced a filmstrip-like anti-alcohol short.
Also starred in one episode of Just Shoot Me as the friend Elliot feels he has an emotional connection. Soon to be found in Finch.
He was a contestant on the game show version of Scrabble under the name Chip Puscar on March 21, 1990, two days before the show ended its first run on NBC.
Esten also had a recurring role on the TV show The Winner, playing the boyfriend of Alison.
He also appeared on the TV show Lois & Clark: The New Adventures of Superman in Season 4, Episode 10 "Stop The Presses" as Ethan Press.
He has just started appearing on ER as orthopedic surgeon Barry Grossman. He appears to be staying on the show longer because he may become a love interest of Parminder Nagra's character.