James Bowen wasn't always a cat person. Before, he was a homeless heroin addict struggling to take care of himself.
But, according to the Daily Mail, when Bob showed up, wounded and ill, little did Bowen know that both their lives would turn a corner.
And it seems they are destined to be together - Bowen, an aspiring musician, and Bob, a ginger cat with a big personality.
They have become a regular sight on the streets of London and Bob has almost tripled the busking income of Bowen, who now has his life back on track.
Their story has already been turned into a best-selling book, and Bowen is now leading discussions to have it turned into a Hollywood movie.
That's a far cry from the days when Bowen was living on the streets.
"When you're sleeping rough, you are surrounded by people doing drugs," he told the Daily Mail.
"They offer you some, saying it will help you sleep - which it does - or make you feel better. And before you know it, you're thinking 'Why not? I've got nothing else'."
Bowen became so heavily dependent on opiates that on several occasions he almost died.
After three years on the streets, he was given a council flat.
By the time he found Bob, he was in the process of kicking his drug habit with the help of a National Health Service recovery programme.
"He was hiding in my building - he had been attacked by another cat, or maybe a fox. He had a great big wound on his side, the poor thing."
At that stage, Bowen was pulling in a meagre £25 (NZ$48) a week from busking, but the course of antibiotics Bob required cost £28.
Bowen paid, and Bob has been eternally grateful.
Streetcat Bob now has more than 12,000 followers on Twitter. Bowen's book, A Streetcat Named Bob, has sold more than 250,000 copies and been translated into 18 languages, and it has netted the pair £30,000.
Having always lived a fairly nomadic life, Bowen said Bob saved him just as much as he saved Bob.
"I didn't plan to keep him - I thought he was a street cat. So after three weeks, I tried to set him free," he told the Mail.
"I'd take him outside, but he just wouldn't run off. I would leave for a day's busking and he'd follow me up the road. Then, one day, he followed me all the way on to the number 73 bus. He climbed on right after me!"
Bob now has his own photo ID card for the London transport system, and goes busking regularly with Bowen.
"I got him a lead, but he likes to climb up on my shoulders. He just picked it up naturally. He's a genius, really."