Mr Seager, from Aylesbury, Buckinghamshire, said he was driving to a classic car show in Birmingham on Sunday, with friends, when they stopped at a service station in Thame, Oxfordshire.
“We decided to stop and fill up and get some coffees, and I thought I would get a Mars bar,” he said.
“It’s just what I fancied that morning.”
When he opened the bar he showed his friends who had never seen anything like it before.
“I thought, ‘I will take a picture of it for a laugh’, and ate it, and thought nothing of it,” he said.
He uploaded it to the Facebook group, where it has, so far, garnered more than 200 shares and 2,600 comments.