In 1988, Melendez attended New York University's film school, and belonged to a band called "Rock Slide." His college roommate, Comedian Mitch Fatel, was on the verge of quitting his internship with The Howard Stern Show, when Melendez asked him for a recommendation for an internship there. The show's Producer, Gary Dell'Abate, mentioned Melendez's stuttering to Howard Stern who, without seeing him and even before he was interviewed, told the Producer to hire him.

Melendez started receiving national exposure in the early 1990s as Stern's syndicated morning radio show acquired more markets and in 1994 when its condensed version began airing nightly on E! Entertainment Television, a basic cable network with national coverage. During his 15-year run as Stern's employee, Melendez also starred in the Off-Broadway show Tony n' Tina's Wedding where he met his wife, Suzanna. He appeared in such films Airheads, Meet Wally Sparks, Dude, Where's My Car?, Osmosis Jones, as well as Howard Stern's film Private Parts. He has also appeared on television in episodes of Wings, Baywatch Nights, and the 2003 United States version of the reality series I'm a Celebrity... Get Me Out Of Here!.

Melendez was also the protagonist of some of the show's more outrageous moments. In 2001, during A.J. Benza's appearance, Melendez got slapped in the face by Benza who did not appreciate the incessant lampooning of his failed late-night show, seeing Melendez as the main culprit. The on-air slap prompted extended fracas and it resulted in Benza being permanently banned from Stern's show.

Throughout the early part of 2002, Melendez and WXRK afternoon deejay Lee Mroszak (aka "Crazy Cabbie") had numerous on-air spats, which were used by Stern as fodder for multiple segments on the show. Their feud eventually culminated in a boxing match scheduled for Friday morning May 31, 2002 at Trump Taj Mahal in Atlantic City and was promoted on the show as "The Flunky versus the Junkie" with 2,500 tickets going on sale for $100 each. The 7 am fight, essentially an extended segment on the show which itself was broadcast from around the ring that morning, was set for five 2-minute rounds with a two-minute break in between each round and it went the distance with the 175 lb Melendez winning over the 262 lb Cabbie by unanimous decision.

In parallel with his duties on the Stern show in the morning, Melendez got a daily afternoon show on New York City's WXRK (The Howard Stern Show flagship station) from noon to 1 pm called Out to Lunch, consisting mostly of taking musical requests by e-mail and playing them. The show was cancelled on August 21, 2003 with Stern turning it into a 45-minute segment at the end of his live broadcast that day by having WXRK program Director Robert Cross (aka Chuck Roast) come in and break the bad news on the air to Melendez.

After moving to California in 2004 to work on The Tonight Show, Melendez resided in the city of Calabasas with his wife, Suzanna Keller, and their three children. The couple filed for separation in October 2011 and divorced in 2012.

On February 27, 2008, more than four years removed from his time on The Howard Stern Show, Melendez was interviewed over the phone by Adam Carolla on his radio show with discussion of Melendez's 15 years as Stern's employee dominating the conversation. Carolla brought up the fact that on-air personnel on radio shows, even long-running hit shows, earn very low salaries compared to the show's host and wondered what kind of money Melendez made considering he was down in the show's pecking order, behind Stern, Robin Quivers, Fred, Jackie, and Gary. Melendez revealed that his first salary on The Howard Stern Show in 1990 was $10,000 per year before adding that, much to his disappointment, he only got an additional $10,000 per year once the show began to be broadcast on E! in 1994.

In September 2009, Melendez reunited with Leno and former Tonight bandleader Kevin Eubanks as a member of the writing staff on The Jay Leno Show. Confirmation of his status on Leno's new prime time show came later than that of Eubanks, weeks after the end of Leno's tenure on The Tonight Show, which led to speculation that he would not appear at all. Melendez's ambiguous job status prompted a sarcastic job offer from his former boss Stern.

With the return of Leno's Tonight Show in March 2010, Melendez continued in the writing role, which he continued on The Jay Leno Show. Melendez did not return as an announcer on the second incarnation of The Tonight Show with Jay Leno (the job went to Wally Wingert) and was employed as a staff Writer and occasional on-air segment host until Leno's departure from The Tonight Show on February 6, 2014.

On November 4, 2015 Melendez announced that he had become the executive Producer and an on-air contributor to The Stephanie Miller Show, a progressive radio talk show. His role was later reduced to one hour per week on Fridays, and as of fall 2016 he is no longer part of the show.