As we celebrate Sylvester Stallone's 78th birthday today, Rocky II is back on TV screens tomorrow, featuring Apollo Creed. The Master of Disaster was probably Rocky's greatest opponent, not only for their lengthy antagonism in the ring, but also for the impact they had on each other's lives.

When actor Carl Weathers died in February this year Stallone said: "It's a horrible loss. He was magic, and I was so fortunate to be part of his life... We lost a legend yesterday. My life was forever changed for the better the day I met Carl Weathers."

But, things between the two macho actors were a little, ahem, 'rocky' right from the start, when Weathers auditioned for a movie created by a little-known actor. Both were passionate, strong characters, and, in the heat of the moment, real-life aggression exploded between them when they were filming a crucial scene and turned into physical violence.

Stallone later revealed that the beating he took left him with "enlarged intestines, rearranged insides..."

It all kicked off long before filming began when Weathers went for his first audition, he said: "There was nobody to read with, and they said you’re going to read with the writer... And we read through the scene and at the end of it, I didn’t feel like it had really sailed, that the scene had sailed, and they were quiet and there was this moment of awkwardness, I felt, anyway.

"So I just blurted out, ‘I could do a lot better if you got me a real actor to work with.'" Of course, he hadn't realised that Stallone hadn't just written the script: "So I just insulted the star of the movie without really knowing it and not intending to."

Luckily, Weathers described how Stallone recognised that this kind of fighting spirit was perfect for the role: "Sometimes the mistakes are the ones that get you the gig."

The highlight of Rocky II is the titanic fight between the two sluggers. Stallone came into the scene already suffering a workout related injury after a 220-pound weight fell and tore his right pectoral muscle. He also meticulously plotted out the fights in every movie, but this all spiralled out of control when passions exploded in the heat of the moment and the two actors started pushing, shoving and verbally attacking each other for real.

Weathers landed some punches that he was supposed to pull and Stallone recalled: "I took a terrible beating. I let Carl Weathers really pound me. It was the most gruelling thing I've ever been through. Broken bones, the works... A lot of those shots aren't faked. It's as hard to learn not to hit somehow as to hit them, Right now my health is pretty bad."

Stallone, however, again realised that the authenticity was electrifying on screen and let the action roll and explode on screen.

Not that Weathers escaped unscathed. He was sidelined in agony for four days after Stallone accidentally landed a brutal blow to the lower body.

The two stars built a friendship offscreen as their characters bonded on screen until Creed was felled by Drago in Rocky 4, with Stallone later admitting: "If I had to do it over again I never would have killed Apollo. Absolutely not. It was foolish. I thought I needed that kind of springboard to protect the drama on this really great, power velocity forward."

Even so, Creed almost made a final return to the screen in a flashback for 2006's Rock Balboa, but Stallone summarily dropped Weathers. He explained that year: "Apollo Creed is not in Rocky Balboa because he wanted many thousands of dollars for a two-second piece of he and Rocky boxing. Unfortunately, we couldn't afford it. Whatever happened to loyalty? Apollo Greed?" 

ROCKY II IS ON ITV 4 ON SUNDAY AT 8PM