The trainer who looked after Marcel the Monkey on early episodes of Friends has hit back after David Schwimmer said he did not enjoy working with his simian co-star.

Schwimmer, who played Ross Geller on the long-running sitcom, kept the unruly capuchin monkey as a pet in the first season of the show and he has made it very clear that he was no fan, telling Entertainment Weekly in 1995, "I hate the monkey".

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The actor also returned to the subject on the recent Friends reunion special and said that the monkey, who was played by two monkeys named Monkey and Katie, often didn't behave as he was expected to.

"Here is my problem: The monkey, obviously, was trained. It had to hit its mark and do its thing right at the perfect time," Schwimmer said.

"What inevitably began to happen was we would all have choreographed bits kind of timed out, and it would get messed up because the monkey didn't do its job right. So, we would have to reset, we'd have to go again, because the monkey didn't get it right."

Now monkey trainer Mike Morris, who says he worked on "about five episodes" of Friends has suggested that Schwimmer may have been jealous of the attention Marcel received on the show.

Speaking to The Sun, Morris said, "This is just my opinion... [but] the first couple episodes [Schwimmer] was pretty friendly with the monkey, and after that, the monkey was getting a lot of laughs, and either it was throwing him off or [he was] getting a little jealous. I don't know. One of those two things."

He added, "It is true that we prefer that actors don't become too friendly with the monkey. An actor is a prop to the monkey and has to work with that prop.

"We don't want them to become friends because then [monkeys] think, 'Oh, it's my friend, I don't have to work… They just want to go hang out with their friend instead of doing what they're supposed to do. It's not out of spite or malice."

Morris also said that Jennifer Aniston and Matt LeBlanc, who also shared scenes with the monkeys, were "a pleasure to work with".

The capuchin called Monkey recently died of cancer, but Katie is still working.

"So Schwimmer was talking ill of the dead when he made those comments [on the reunion]," Morris continued.

"I find it despicable for him to still be speaking ill of her. Him still talking ill about the monkey all these years later seems pretty childish to me… It was one season over 25 years ago, it's time to let it go."

Morris added he never watched Friends or the reunion because of the actor.