Sometimes rivalries in football go so deep that opposing fans only speak to each other in abusive taunts. It's all about the passion for one half of a rivalry, and the other crowd aren't even referred to by name.
But how far would you go if you needed money for your child's treatment? Would you get a tattoo of your rival teams crest to raise money?
That's exactly what 38-year-old Manchester City fan Mark Pinder did. His 12-year-old son Kirk has muscular dystrophy which means that his muscles are slowly deteriorating. Unfortunately there is no cure.
That's not exactly what a father wants to hear, so he decided to raise money for the Duchenne Now charity to research muscular dystrophy. He pledged that if he raised £10,000 he would get the a Manchester United crest tattooed on his leg.
And boy did he follow through:
Does the Manchester City fan have any regrets? Of course not. "I’m buzzing now I’ve done it." Pinder told the Independent.
I’m quite happy with the tattoo now because it’s a good memory to remind me of all the money I raised.
I’m so proud to have made £10,000 and I’ve loved the whole fundraising experience. It’s been crazy to see how the community rallied together and it was humbling for people who don’t know me to take an interest and donate to the cause.
You can support Mark and Kirk through their Just Giving charity page here. or text text DNOW60 to 70070.