It’s certainly not the first time that Morgan has taken aim at a fellow celeb on social media.
And while his jab at Theroux was all in fun, he's been in more than his share of spats over the years.
We have a look at some of his biggest feuds, as well as his recent run-in with Theroux.
Morgan has had a light-hearted pop at Theroux, after the documentary-maker claimed he could beat him in a fight.
TV star Theroux made the claim in his Interviews series as he chatted to boxing star Anthony Joshua in the first episode.
Talk had turned to who Theroux could fight if he ever got into the ring himself and Morgan’s name came up.
— Piers Morgan (@piersmorgan) November 8, 2023
Theroux thought it could be a good match saying: “He’s very famous… and I think I could take him.”
The broadcaster then responded on X, joking: “Have you lost your marbles, @louistheroux? I’d destroy you in 30 seconds, you puny wastrel.”
Cheeky Theroux didn't stop there as he hit back at Morgan on X.
I don't think you've got the cardio fitness, Piers, TBF. You'd gas out and after that I'd just be playing music on your chin like a boxing Beethoven.
— Louis Theroux (@louistheroux) November 9, 2023
He wrote: "I don't think you've got the cardio fitness, Piers, TBF. You'd gas out and after that I'd just be playing music on your chin like a boxing Beethoven."
Will Morgan have a good comeback?
Morgan and Clarkson feuded for years, with things even turning physical.
The trouble seems to have started in 2002 when Morgan was editor of the Mirror and had published photographs of Clarkson that he wasn't pleased with.
Then the following year, they ended up sat next to each other on a Concorde flight and the Grand Tour star got his own back.
Speaking on his show Who Wants To Be A Millionaire?, he said: "I was on its last commercial flight they sat me next to the lavatory, or Piers Morgan as you know him. I poured a glass of water over his crotch, so when he got off, it looked like he’d wet himself."
Then in 2004, Clarkson hit Morgan at an awards ceremony.
Speaking on the Big Fish podcast earlier this year, the former Good Morning Britain (GMB) star said: "That scar on my head is where he punched me in the head, we're not exactly best buddies, although we get on fine now."
Morgan said he could have “played the victim” after the altercation, adding: “But I went, you know what? Fair enough, I'd of probably done the same."
Clarkson later spoke about the brawl during an interview with the late Michael Parkinson, saying it was "the first time I’ve hit anybody ever".
Morgan let rip at both Grant and Steve Coogan in 2019 as they shared their thoughts on the general election.
He wrote on Twitter (now X): “Who gives a flying f***k what Coogan & Grant have to say about this election? Honestly, the stupefying pomposity of these clowns trying to thwart democracy is beyond parody.”
However, Grant snapped back to accuse the presenter’s former paper of phone hacking.
“No journalist who worked for me at the Daily Mirror has ever been charged with or convicted of phone-hacking,” Morgan replied.
The journalist raised the stakes by mentioning the fact that Grant was arrested in 1995 when he was caught in a car with sex worker Divine Brown.
“YOU however have a criminal record for lewd conduct with a hooker in Hollywood,” he said.
“So I suggest you put the halo away, ‘Saint’ Hugh.”
Morgan and McGregor fell out in 2017 after the presenter criticised a women’s march against Donald Trump.
Writing in the Daily Mail, he suggested the feminism message might have gotten a bit lost and claimed some were “whipped into a man-hating frenzy” at the event.
His comments evidently irked McGregor, who then pulled out of an interview with Morgan.
“Was going on Good Morning Britain, didn't realise @piersmorgan was host,” he posted on Twitter.
“Won't go on with him after his comments about #WomensMarch.”
Morgan hit back: “Sorry to hear that @mcgregor_ewan - you should be big enough to allow people different political opinions. You're just an actor after all.”
The pair were both big stars on rival channels and quibbled about who was beating who in the ratings, indulging in what was more of a friendly rivalry than a real feud.
They didn’t wrap it up when Morgan walked out of GMB in 2021 after refusing to apologise for saying he didn’t believe some of the things the Duchess of Sussex said in her interview with US chat show host Oprah Winfrey.
Walker even had a joke about the moment, pretending to storm off set himself over a BBC weather report.
Morgan didn’t take it lying down and bit back: “I'm surprised BBC bosses didn't storm in and drag you off set after yesterday's ratings came in."
However, the pair have since been spotted playing golf together and in 2021 Walker told The Times of his old rival: “He likes to throw a few insults around, but underneath all the froth I think there is a decent bloke fighting to get out."
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