A deaf six-year-old boy's response to Rob Delaney's CBeebies Bedtime Story using sign language has been shared thousands of times online.
Tom McCartney waves his arms and stands up in his chair in excitement as he watches the Catastrophe star on TV.
His mother Laura said Tom, who has complex medical needs, was "enthralled" to see a story told "in his language".
Rob Delaney said he was honoured to become the first person to sign a CBeebies Bedtime Story in Makaton.
The US actor and comedian read and signed Ten in a Bed by Penny Dale last Friday in a first for the popular Bedtime Story, whose previous guest readers have included Dolly Parton, Tom Hardy and Orlando Bloom.
Delaney learned Makaton in order to communicate with his son Henry who had a tracheostomy while seriously ill with a cancerous brain tumour. Henry died, aged two, in January.
Laura McCartney, from Larbert, near Falkirk, said her son's reaction to the bedtime story left her in tears.
"Tom loves books. He really loves books so the Bedtime Story is something we would watch, but he didn't really get what was going on." she said.
"For him it's a person sitting with their lips moving and pictures of the book - so he couldn't really follow it.
"As soon as it came on, Tom's face changed. He instantly knew this was different because someone was talking his language.
"As soon as he saw that Rob was signing his whole face lit up. Enthralled is the word I keep thinking of."
She added: "He couldn't take his eyes off the TV. ...He was laughing and clapping and things, then he would stop and look at me and be like 'Mum, are you seeing this?'
Laura's husband filmed the reaction of their son, who twice stood up in his activity chair, which is designed for children with disabilities.
"He looked like he was going to dive off it at one point which was giving me a bit of a heart attack," said Laura.
"He was so excited - it was a nightmare trying to get him to bed. I've never seen him like that."
What is Makaton?
Makaton is a language programme using signs and symbols to help people communicate.
The signs used in Makaton have been designed to emulate those used in British Sign Language (BSL)
Makaton is always used in conjunction with speech, in order to support spoken language.
The name Makaton comes from the names of its creators, speech and language therapists Margaret Walker, Kathy Johnston and Tony Cornforth who developed it in the 1970s.
It has been adapted for use in more than 40 countries, including Poland, Australia, Greece and Japan.
CBeebies viewers will already be familiar with Makaton through the award-winning Something Special programme, where each episode is signed by presenter Justin Fletcher, aka Mr Tumble.
Both Rob Delaney and children's author Penny Dale commented on the video when it was posted on Twitter.
Delaney posted: "So beautiful. What a wonderful family you are xx"
Penny Dale responded: "This is SO lovely and brilliant that you've captured Tom's excitement unfolding, moment by moment as he follows the story, and it's a perfect example of the power of signing and speaking."
Tom is undergoing treatment for 10 medical issues including the heart defect tricuspid atresia and total deafness.
He was born without an oesophagus and breathes through a plastic tracheostomy tube.
'A wee tonic'
The Bedtime Story came after a particularly difficult week for the family as Tom had been admitted to hospital the previous weekend with a serious chest infection.
"It's hard work, he needs a lot of extra care and sometimes you can get a little bit worn down by that," said Laura.
"I was a bit exhausted and that felt like a wee tonic. I just couldn't believe that in the space of a week we'd gone from an emergency hospital admission and less than a week later he was standing up on his chair, and so excited and animated about this lovely story."
Earlier this year, Tom's parents were moved by hearing Rob Delaney's "beautiful" account of caring for his own son before his death in January.
They hope more children's television will be signed in Makaton in future.
Laura said: "I don't think that signing detracts from the story or makes it inaccessible for people who don't use that form of communication. If anything I think it adds to it."