The 57-year-old had not 'intended to cause serious injury' because it was a bizarre 'family game'. The schoolboy's burns were spotted by staff at his school, who called in social services in Bradford, West Yorkshire.
And yesterday, the granddad – who had been drinking heavily at the time - was convicted of child cruelty and given a 12-month community order.
Solicitor advocate Tom Rushbrooke told a judge at Bradford Crown Court: "It wouldn't be fair to say he had gone out to deliberately burn the child.
"He has played a stupid, idiotic game with his grandchildren, who he worships."
Prosecutor Karma Melly said a teaching assistant at the boy's school noticed that his leg was bleeding and asked him about it. A social worker was then contacted.
Miss Melly said the Crown accepted the injuries were caused as part of a game, but said they were deliberate acts.
Judge Robert Bartfield told the man he had pleaded guilty to an unusual offence but he was dealing with him on the basis that he had been playing a family game, chasing youngsters with a cigarette and sticking the cigarette onto them 'not with the intention of doing them any significant harm, but no doubt with the intention of making them hurt and squeal, which no doubt you would have found amusing'.
The judge told the defendant he had behaved like a 13-year-old. He gave him a 12 month community order, a six-month alcohol treatment requirement and a thinking skills exercise.