All rivalries have exceptions that prove the rule. Take Romeo and Juliet, for example. In the case of the North London football scene, this heart-warming story is more Bromeo and Juliet...
Tim Reid and Dany Reid, no relation, have been friends since childhood. Three years after Spurs fan Tim, 26, was diagnosed with scarring on his kidneys, he required a transplant.
His friend and ardent Arsenal fan Dany stepped up to help, offering one of his kidneys to help Tim get well again.
Tim says he was "overwhelmed" by Dany's offer. "It's going to change mine and my family's lives completely," he said.
Once Dany had committed to help, he visited Leicester General Hospital for a blood test to see if he was a match. "When the results came back, I was at a match and after that I had to go for what is basically a full body MOT."
This consists of numerous blood and urine tests, scans, x-rays and swab tests to ensure Dany was a correct match and was healthy enough to donate to his friend.
The procedure took place last Thursday and both are on the road to recovery. Dany is out of hospital, and Tim is expecting to be released in the next few days.
Although Wales is now trialling an opt-out policy when it comes to organ donation, England, Scotland and Northern Ireland still require citizens to opt-in.
Dany urged people to think about signing up to the organ donor register, saying: "Your body still gets put to rest after they take what they need, but someone, somewhere, will get to live their life properly."
Tim joked: "Dany has grown a heart whilst losing a kidney.
"After the recovery I will be able to live a normal life and go back to playing football."
The pair are also planning to attend the North London Derby together on November 5.
Dany says: "I've got tickets but Tim doesn't want to sit in the Arsenal end!"
Unsurprisingly, both men think their team will finish top of the Premier League this season, and both predict their mate's team will tank to the bottom of the table. The rivalry isn't over, then, even if Dany did give Tim a kidney.