When you support a football team, it's usually because of where you live or who your family support.
Sometimes you might also have a second team that you follow - maybe because you like their players, their shirts, or even because you like the way they play.
It could be a team in a different country, or even a different league. But it's pretty unlikely that you would pick two local rival teams whose fans definitely don't support each other!
Someone needs to let Zac Efron know he can't support Arsenal AND Tottenham!
Do you think it's OK to support two rival teams? Let us know what you think in the comments below.
The Greatest Showman star was spotted at the match between Tottenham and Brighton on Tuesday, but which of the London rivals does he really support?
He was seen wearing a Spurs shirt - no surprise there.
But in the past he was spotted wearing the shirt of their huge north London rivals - Arsenal - when he went to see them play Chelsea.
Now maybe we should give Zac a bit of a break. Football - or soccer - isn't as big in the United States as it is in Europe.
But still, even in the US people get the idea of not supporting two deadly rivals in American football, baseball or basketball.
Maybe he doesn't actually support either team, but just likes to buy a shirt of the team he's going to see.
During the 2016 Rio Olympics he went on a TV show wearing his Team USA shirt.
That's more like it, Zac!