Though originally from Dublin, Ireland, most of Quinn's roles have called for him to hide his Irish accent and don an American one.

The WB series  "Angel" (1999/I) was his first role in an American series where he was allowed to use his own brogue.

Quinn's first screen kiss was in Shout (1991) with Gwyneth Paltrow. While still playing Mark on "Roseanne" (1988), Quinn also took a role as youngest son Cedric on a series called "Covington Cross" (1992). But while "Roseanne" (1988) filmed in the US, "Covington Cross" (1992) was filmed in England, which gave the actor one hell of a commute.

Was a co-owner of Goldfingers, a 007 themed nightclub in Hollywood.

Attended Clonkeen College, a Roman Catholic Christian Brothers school, in Blackrock, near Dublin.

Had a tatoo "Erin Go Bragh" (Ireland Forever) on his right shoulder, and a Harp on his left.

Did dead-on impersonations of "Sesame Street" (1969)'s Grover and Christopher Walken.

His character Mark Healy on "Roseanne" (1988), was intended to be a one-episode guest appearance, but became a seven-year stint.

He was spotted by casting director Johanna Ray, who helped him get representation.

His father Murty, is a musician who played with Dickie Rock and the Miami Showband, and later The Sands with Tony Kenny.

Favorite band was U2.

Had two sisters - Sonya and Louisa.

Worked in a factory, painted houses and waited tables before getting discovered.

Liked hiking, soccer, motor sports and playing the drums and guitar.

He died at a friend's house when he overdosed on heroin.

Actor Michael Fishman, who co-starred with Quinn on Roseanne, set up a memorial fund in his name.

Grew up in Cabinteely, Dublin, Ireland down the street from Cinematographer / Producer Noel Donnellon and Animator / Director Paul Donnellon.

Was good friends with David Boreanez and Christian Kane of Angel.

Both recall on the Season 5 DVD commentary how hard and emotional it was for them to use the name Doyle for Christian's character and how much they miss him.

Though allowed to use his native Irish accent in the show "Angel" (1999), it was so thick that he had to occasionally "Americanize" it so you could understand what he was saying. This sometimes made it sound as if is accent was fading in and out.