In the 1970s, Moschitta attended Nassau Community College, where he appeared in a production of Room Service alongside Nassau alum, Billy Crystal. Moschitta was also once a contestant on the game show, $25,000 Pyramid, where he was paired with comedian Joan Rivers. During the 1980s, he made several appearances on Sesame Street.
Employees of Ally & Gargano hired Moschitta for a spot after seeing him in the ABC TV series That's Incredible! In 1982, Moschitta appeared in the "Fast Paced World" ad for Federal Express, created by Joe Sedelmaier, as a fast-talking executive who apparently keeps up his pace all day long, no matter what he is doing. Advertising Age ranked the ad no. 11 among the top 100 advertising capaigns of the 20th century.
He is well known for his Micro Machines television ads, where he would speak very fast and end each one with the slogan "If it doesn't say Micro machines, it's not the real thing". In later commercials for Micro Machines, however, Moschitta spoke at a slower rate of speed but kept the notable ending tagline.
John "Mightymouth" Moschitta recorded a humorous take on 10 classic novels in which he summarizes each book's entire story in approximately one minute. Included in this collection, entitled Ten Classics in Ten Minutes, is Herman Melville's Moby-Dick; William Shakespeare's Romeo and Juliet; F Scott Fitzgerald's The Great Gatsby; Margaret Mitchell's Gone with the Wind; and John Steinbeck's The Grapes of Wrath. Soon after, he followed up with a second recording, Ten Minute University, in which he rapidly delivers humorous 60-second lectures on various subjects such as comparative literature, physics, economics, and psychology. Originally released on audiocassette in the 1980s, both recordings were re-released on CD in 2004, with accompanying books. In a similar case, Moschitta guest-starred on a Saved By The Bell episode in 1989 as George "Terrible" Testaverde; a teacher who conducts lectures in speed-talk.
In 1990, Moschitta appeared in a commercial endorsing a board game called "Motor Mouth" where the object of the game was to speak a sentence or saying before a timer expired. Moschitta was seen spoofing his famous speed talking ability as he cannot properly pronounce a sentence quickly and gets frazzled at being unable to finish in time.
He was the announcer for the final season of Hollywood Squares, as well as the short lived game show Balderdash. He also appeared on the 2007 game show Identity, first aired on 23 March. He has appeared in I Love the '80s 3-D where he summarized each year's events in mere seconds.