LEGO filmed the man's son, Hsiao Feng, sharing a glimpse of his imagination when building a scene with his bricks.
The boy, from Taiwan, explained his dad repairs and sells cars. He used his LEGO to build a strong car that would be "unbreakable".
"I will give this car to my dad, and he will never have to repair it," he said.
"And he wouldn't be so tired anymore."
For LEGO's 'Gift For Imagination' film, the brand gave Hsiao Feng's explanation of his LEGO toy airtime in adverts across TV, the internet and on billboards.
The company also arranged for the clip to be played on the side of a building by Hsiao Feng's dad's workplace, just as finished work one evening.
As the dad left work, he recognised Hsiao Feng's voice coming from the huge billboard screen above him.
He teared up as he heard his son speak.
"He has always been very imaginative, but I never thought he would use his imagination with the purpose of sharing my burden," the dad said.
"I can truly feel his affection, Hsiao Feng, thank you for always wanting to leave the best for me.
"I promise to spend more time with you and fill you childhood with the best memories.