Danny Lee "Nitro" Clark (born May 21, 1964) is a professional athlete, television personality, author, actor, and producer. He is best known for his role as gladiator Nitro on the TV show American Gladiators. He is also an in demand health and fitness expert and the creator of the "Gladiator Rock'n Run". Dan makes a guest appearance on Married... with Children as Biff, a parachute diving instructor, in the Season 6 episode "The Mystery of Skull Island".