Los Angeles: Actor Jamie Costa has impersonated late actor Robin Williams's characters in a video which has gone viral.In the video posted on YouTube on Monday, Costa impersonated not less than 20 characters essayed by Williams in his 38-year-long career.In the video entitled "Never Had a Friend Like Him", Costa is seen performing impressions of the late actor's most famous characters, including Mork from the TV series "Mork & Mindy", the Genie from Disney's "Aladdin", Teddy Roosevelt from "Night at the Museum", Alan from "Jumanji", and radio DJ Adrian Cronauer from "Good Morning, Vietnam". There are also glimpses of movies like "Mrs. Doubtfire", "Fern Gully", "Flubber", "The Birdcage", "Popeye", and "Good Will Hunting", reports aceshowbiz.com.After posting the video on YouTube, the actor paid tribute to his favorite actor by sharing it on his Facebook page. Costa captioned the video: "My Robin Williams tribute. Never had a friend like him #RIP #RobinWilliams."Some commenters felt that Costa should be cast in a biopic as Williams.With IANS