The 72-year-old, who played Mike Baldwin for 30 years, asked producers if he could be in the background when they filmed scenes for a girl gang fight storyline.
His character, whose final scenes aired in April 2006, died from a heart attack in the arms of Ken Barlow (William Roache).
A source told The Sun: "They were filming in Johnny’s local and everyone was stunned to see him.
"They went over to chat and Johnny asked if he could stay in the background drinking - he thought it would be funny.
"But they said there was no way he could be in shot as they would get in trouble, so he went home with a takeaway."
The insider added: "Johnny's always had a sense of humour - but we couldn't raise Baldwin from the grave."