Mario Lopez Jr. has appeared on several television series, in films, and on Broadway. He is known for his portrayal of A.C. Slater on Saved by the Bell and Saved by the Bell: The College Years. He has appeared in numerous projects since, including the third season of Dancing with the Stars and as host for the syndicated entertainment news magazine show Extra. He has also hosted America’s Best Dance Crew for MTV. In 2012, he co-hosted the second season of American version of The X Factor with Khloé Kardashian, and was the sole host for the third and final season.
Lopez began acting in 1984, when he appeared as younger brother Tomás in the short-lived ABC comedy series a.k.a. Pablo. That same year, he was cast as a drummer and dancer on Kids Incorporated from three seasons. In March 1987, he was cast as a guest star on the sitcom The Golden Girls as a Latino boy named Mario who faces deportation. He was cast in a small part in the movie Colors (1988) as Felipe’s friend. In 1989, Lopez was cast as A.C. Slater in the television Saturday-morning series sitcom Saved by the Bell, a role which lasted five years (1989–1993).
In 1997, Lopez starred as Olympic diver Greg Louganis in the television movie Breaking the Surface: The Greg Louganis Story. The following year, he was cast as Bobby Cruz in the USA Network series Pacific Blue for two seasons before it was cancelled after the fifth season; he then went on to guest star on Resurrection Blvd., Eve, and The Bad Girl’s Guide. In March 2006, Lopez joined the cast of the daytime soap opera The Bold and the Beautiful playing the role of Dr. Christian Ramirez. On July 18, 2006, he was released from his B&B contract. Later that year, Mario guest-starred as a plastic surgeon who drives Christian Troy to jealousy when he sees him naked in the shower in an episode of FX Network’s Nip/Tuck during the show’s fourth season, which began in Fall 2006. He also made an appearance on George Lopez as a police officer in late 2006. Lopez also guest-starred as a reporter for Extra Sesame Street in the Sesame Street episode “The Veggie Monster” in 2012.
Lopez and Courtney Mazza have a reality show on VH1 called Mario Lopez: Saved by the Baby which premiered on November 1, 2010. In the fall of 2006, Lopez signed on as a contestant on the third season of Dancing with the Stars on ABC with professional partner and then-girlfriend Karina Smirnoff who was making her series debut. They finished in second place, losing to the team of Emmitt Smith and Cheryl Burke.
In August 2014, Lopez began hosting the Hot AC edition of the iHeartRadio Countdown.
On February 4, 2015, Lopez reunited with Mark-Paul Gosselaar, Elizabeth Berkley, Dennis Haskins and Tiffani Thiessen on The Tonight Show Starring Jimmy Fallon, where they appeared in a Saved by the Bell sketch with Fallon.