A seven-year-old boy who was born without a right hand said he was thrilled with his new "robot arm".
Louie Morgan-Kemp of Swavesey, Cambridgeshire, collected his Ironman-themed Hero Arm this week.
He had just started fundraising for the prosthetic when a kind-hearted businessman saw his story and offered to pay the full £13,000 cost.
The boy's mother, Hannah Morgan, said "it was all he spoke about" before the summer holidays.
Billy Dixon, 73, from Egham, Surrey, read about the family's fundraising in the news and contacted Louie's mother on Facebook, offering to pay in full.
Mr Dixon said: "I couldn't think not to do it, it's just in my nature doing things like that."
Louie is able to munch on crisps more easily thanks to his new gadget
Louie uses muscles in his arm to press buttons inside the sleeve, which then moves its mechanical fingers.
He said the gadget, made by Bristol-based Open Bionics, helped him pick things up, cut food and pour drinks.
Louie used the arm to drink lemonade from a glass and hold a bag of crisps, using his left hand to eat them, as he got to grips with it on Wednesday.
He said it was "exciting" to get the arm and he was "happy" that Mr Dixon had paid for him to get it.
Ms Morgan said the school summer holidays had been "all about waiting" for his new arm.
"People have said how cool it is," she said.
Seven-year-old Louie Morgan-Kemp said he dreamt of doing "stuff other children can do"