Comedian Jason Manford claims to have uncovered a shocking secret - that Fireman Sam has a love child.
Jason, who as a dad of five is a regular viewer of children's TV, reckons Sam is the father of Norman Price.
Naughty Norman is the seven-year-old boy who frequently causes the fires in Pontypandy that Sam is called out to deal with.
Norman has a mum, Dilys, but she's single and no mention is ever made of his dad.
Then Jason drew attention to the lad's hair colour being suspiciously similar to Sam's.
Jason told listeners on his Absolute Radio show: "Let me tell you my little fan theory on Fireman Sam. This is going to blow your mind.
"Norman is the only ginger in the village...."
His radio show guest, former Corrie star Sally Lindsay, corrected him: "No, Fireman Sam's ginger!"
Jason replied: "Exactly! Yes!"
Sally said: You've just blown my mind. "That's why he looks after him and doesn't kill him! It's his son!"
Jason: "And that's why Norman is starting all the fires, it's just a cry for help."
Sally: "He just wants his dad... just a cry for help. 'Love me, daddy.'."
Jason: "And that's why he's such an Asbo kid."
Other parents on the internet agree with Jason's theory, as threads on Mumsnet and Netmums reveal.
On Mumsnet, McKayz wrote: " I'm just watching Fireman Sam with the boys.
They both have the same hair, Dilys always seems to blush when Sam is around and Norman never gets in trouble for any of the stupid and dangerous things he does."
Princess Teacake said: "I always thought that Norman saw Sam as a father figure and all his troublemaking is a desperate cry for attention."
On Netmums, Katie M wrote: "My brother says this all time.
He reckons he's his secret love child."
"As Sam and Norman are the only gingers in the village and Norman has no dad to speak of."
Jodie M agreed: "Somebody told me that Fireman Sam now lives with Norman and his mum, and when he took his hat off he had red hair making the point that they were father and son."