Most of the time, actors gush about each other, so it's rare to hear one slamming another, especially to the media. But that’s what happened this weekend at San Diego Comic-Con, when Freddie Prinze Jr. openly dissed former 24 co-star Kiefer Sutherland.

Prinze, who was promoting his animated series Star Wars Rebels, told ABC News that Sutherland was such a nightmare to work with that he "just wanted to quit the business after that."

Prinze grew up in the industry (his father was an actor) and started acting right out of high school. He became a teen heartthrob thanks to I Know What You Did Last Summer and She's All That before growing into heavier roles, like on 24. Little did he know that what seemed like a plum, high-profile job would go so sour.

"I did 24, it was terrible. I hated every moment of it," Prinze said. "Kiefer was the most unprofessional dude in the world. That's not me talking trash, I'd say it to his face, I think everyone that's worked with him has said that."

"Kiefer worked with Freddie Prinze Jr. more than five years ago, and this is the first he has heard of Freddie's grievances," a rep for Sutherland said in a statement to Yahoo TV. "Kiefer enjoyed working with Freddie and wishes him the best."

While not everyone has commented as publicly as Prinze, there have been other rumblings about Sutherland's difficult behavior on set. Oscar nominee Shohreh Aghdashloo, who joined the cast in Season 4, believes her character was killed off unexpectedly because she clashed with Sutherland.

"I'm afraid working with him proved to be hard. That young man was pretty angry," she told Fox & Friends.

Prinze’s problems with him apparently stemmed, in some part, from their height difference. After 24, he worked as a producer and director for WWE’s Vince McMahon.

"At least he was cool and tall. I didn't have to take my shoes off to do scenes with him, which they made me do," Prinze said. "Just put the guy on an apple box or don't hire me next time. You know I'm 6 feet and he's 5'4."(Note: according to most reports, Sutherland is described as 5-foot-9.)

Not all of Sutherland’s co-stars think he’s difficult. On The Late Late Show in 2002, Elisha Cuthbert (who played Jack Bauer’s daughter on 24) said the actor was serious, but professional. And young David Mazouz, who played Sutherland’s son on Touch, raved about how “patient and kind” he was.

But it’s very telling to hear what Mary Lynn Rajskub, who starred as Chloe O'Brian on 24 for seven years, has said about the actor. On Marc Maron’s podcast, the actress was diplomatic, but gave indications that his reputation might be true.

"Kiefer and I like each other; I would go so far as to say we love each other in that respect," she said. But then, she added that they'd never really developed a personal relationship — despite working together for seven years (plus the time from 24: Live Another Day).

Much of the cast and crew became like a family, she noted, "But we never fully hung out or fully had a conversation the entire time."