Real Monsters, Doctor Doom, Wrecker, Sabertooth and others in The Super Hero Squad Show, MODOK in various Marvel media, Cobra Commander in GI Joe: Resolute and Renegades, Starscream in the Transformers film series, Mr. Whiskers of Disney's Brandy & Mr. Whiskers, the titular characters of Cartoon Network's Cow and Chicken along with its main antagonist, The Red Guy, Professor Monkey-for-a-Head in Earthworm Jim, I.R.

Growing up, Adler was a self-described "TV junkie",[4] and an avid fan of Rocky and Bullwinkle, The Three Stooges and Irene Ryan's Granny Moses from The Beverly Hillbillies.

[5] During this time, he worked a variety of jobs, including waiter, janitor, paper delivery man, floor stripper, house painter, remedial reading teacher and caretaker for an Episcopal church.

In 1984 and 1985, he starred as Arnold Beckoff in Torch Song Trilogy, for which he was nominated for the 1985 Helen Hayes Best Actor Award, in New York City before moving to California in 1986.

[4] His voice acting career took off when Adler landed the roles of Nat Smurfling in the fourth season of The Smurfs, "Rowdy" Roddy Piper on Hulk Hogan's Rock 'n' Wrestling, Silverbolt on The Transformers and Eric Raymond, Techrat and Zipper in Jem.

In an interview for The Magic Behind the Voices, Adler commented on the experience: "you spend your whole life going, "God, I just want to be in a TV show and have a parking space".

Joe, Mr. O'Greasy on A Pup Named Scooby-Doo, Deputy Fuzz and Tex Hex on Bravestarr, Cavey Jr. on The Flintstone Kids, Pinky Dalton on The Good, the Bad, and Huckleberry Hound, Quark and Zappy on Rockin' with Judy Jetson, the TurkeyBoy and sometimes Hamburglar in McDonald's commercials and The Wacky Adventures of Ronald McDonald, Mad Dog, Hacksaw, and Howard Huge in TaleSpin, Dripple on Tom and Jerry Kids, and the titular character on Paddington Bear.

[6] Producer Tom Ruegger recalled that he and voice director Andrea Romano insisted Steven Spielberg cast him due to the "great deal of energy" he brought to Buster.

[12] His subsequent credits as voice director include Nickelodeon's Blaze and the Monster Machines, Wabbit (season 1), Kulipari: An Army of Frogs and Kung Fu Panda: The Paws of Destiny.