Nowadays, of course, we know him from America's Got Talent (one of my favorite shows) but back in the 80s and 90s he was a stand-up comedian and a TV and movie star!
Here's his Wikipedia article:
"Mandel came to national attention in the US during a six-year run on St. Elsewhere, starting in 1982 and playing the role of Dr. Wayne Fiscus, opposite the late Ed Flanders, and Norman Lloyd, with whom he remains good friends as of 2015. While working as Dr. Fiscus, and continuing to work as a comedian, he also did movies, including his role as the voice of Gizmo in the 1984 hit Gremlins and its 1990 sequel Gremlins 2: The New Batch. In 1985, Mandel made a cameo in the Michael J. Fox directed short "The Iceman Hummeth" which was subsequently broadcast on Late Night with David Letterman in November 1985. In 1986, he starred in A Fine Mess alongside Ted Danson. He performed his stand-up comedy act in several cities (the Watusi Tour), which was followed by his Watusi music video in 1987. For the first two seasons of Muppet Babies, he voiced Bunsen Honeydew, Animal, and Skeeter. He starred on the 1987 comedy film Walk Like a Man. He was also "Maurice" in the 1989 movie Little Monsters. In 1990, he starred in the short-lived sitcom Good Grief on Fox. He was also the creator and executive producer of the Emmy-nominated children's animated series Bobby's World (1990–1998), to which he supplied the voices of the title character and his father (using Howie's "normal" voice for Bobby's dad). Bobby's World ran for eight seasons on Fox and was later syndicated..."
"In 1994, Mandel voiced the lead character, Little Howie, of the video game Tuneland. He starred in the sketch comedy series Howie Mandel's Sunny Skies in 1995 on Showtime. Mandel appeared in the 1995 Clint Black country music video "Summer's Comin'". He played the lead role of the professor in the short-lived TV series The Amazing Live Sea Monkeys, and guest-starred on a 1996 episode of the ABC TV series Lois & Clark: The New Adventures of Superman as DC Comics supervillain Mister Mxyzptlk. In 1998, he hosted his own syndicated talk show, The Howie Mandel Show, which was cancelled after one season. In 1999/2000, Mandel played "Jason" in the film Apocalypse III: Tribulation..."