Jimmy Carr is renowned for his close-to-the-bone jokes - but even he realised he had crossed the line when he targeted Professor Stephen Hawking.
The comedian faced backlash recently over a 'sickening and unacceptable' Holocaust 'joke' featured in his Netflix stand-up special 'His Dark Material'.
He admitted he was worried he was 'going to get cancelled' for the derogatory line which made reference to the almost half a million Roma and Sinti people murdered in Nazi death camps.
The funnyman has been slammed in the past for comments about dwarfism, abortion and Paralympians - however one of his cruelest jokes was actually made offstage, according to the Mirror.
In a strange attempt to be funny, Jimmy sent what he described as an "insane letter" to Stephen Hawking, who sadly died in 2018 aged 76.
Claiming it was a "well-worn comedic device" to send a prank letter, Jimmy wrote to Stephen claiming his son shared a similar condition - along with a vile insult.
Stephen suffered from motor neurone disease, an incurable illness that left him in a wheelchair and only able to speak through a computer controlled machine.
Jimmy sent out the "brutal" letter in the hope of getting a response from Stephen, but got way more than he bargained for.
Claiming he had a nine-year-old son, Jimmy said he wrote: "He is severely disabled and has similar limitations to you. But equally he has a great spirit and refuses to give in on a world all too ready to dismiss him as a four-eyed, monotonal voice boxed, wheelchair-bound freak.
"Anyway what he'd really like to know is can you come over and play?"
But Jimmy was left red-faced when he got a phone call from Stephen's assistant, who inquired as to the name of his fictional 'son'.
Jimmy made up a name and lied about his supposed son's disability, then two weeks later got a "beautiful" letter back from Stephen himself along with his biography and photo.
Apologising for not being able to come and see him, Stephen wrote: "You're never too old to play but I'm afraid I'm very busy. Here's a balloon ride, maybe he'd like to go on one. I went on one recently; they can put a wheelchair in the basket."
Jimmy admitted he felt like "the worst person in the world" when he discovered Stephen had bought Jimmy and his imaginary 'son' a balloon ride.
During one of his tours, he said: "It's all a bit clever sending people letter and running away but that one went horribly wrong.
"I also thought it demonstrated that Stephen Hawking is not only a brilliant man but a brilliant bloke. What a lovely thing to do."
A few years later, guilt-ridden Jimmy bumped into Stephen at an awards ceremony and finally came clean about the letter.
The day after, Jimmy got an email from Stephen inviting him for tea in Cambridge and they chatted for a couple of hours.
They formed quite the friendship, with Jimmy bringing the cosmologist to a number of his shows and taking him out for dinner.
Last year, he told the Daily Mail: "Everyone wanted to meet him. He used to come to my parties and I remember Elton John being really excited to talk to him. Everyone is secretly really into physics."
When they weren't watching a musical or eating curries, the pair liked partying together and Stephen would regularly get on the shots.
"I think if you have a friend that’s tetraplegic you have to be quite chatty, because obviously the typing takes him so long," he told the Irish Times in October last year.
"We’d do shots together sometimes too. His care team said tequila would be too much, so he’d be on the Cointreau."
There was even one strange evening where Stephen was doing shots with Jimmy, football pundit Jamie Redknapp, former cricketer Freddie Flintoff and singer Harry Styles.
"When Stephen Hawking was drunk, there was no difference. I guess the voice modulator doesn't have a 'slur' setting," joked Jimmy.
The comedian said that Stephen's motor neurone disease didn’t stop him from working the room at the A-list bashes.
"His care team were so amazing because they’d been with him for years and they knew when he was bored. They could just tell," he said on the Spit or Swallow podcast.
"And if you were talking to him they’d be able to tell his anecdotes."
Sadly, Stephen died peacefully at his home in Cambridge in March 2018 at the age of 76.
Upon his death, Jimmy described Stephen as "not only a world renowned physicist & all round genius [but] he also had a wicked sense of humour."
He has fond memories of the time he spent with Stephen and is often reminded of his friend.
Jimmy said: "Whenever I'm tempted to complain about any little physical malady, I think of how grateful my friend Stephen would've been to have the opportunity to pull a hamstring."
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