The first time I met my Bride's siblings, I was doing everything in my power to fit in. I noticed her brother was wearing a Miami Dolphins hat. Made the comment - is that your favorite baseball team? Her brothers were horrified. Her sisters were thrilled that I did not know either baseball or football.
I was once invited to a Super Bowl party, and I thought sure, I'll come. So I went, and watched the game for a bit on the big TV. I was asked, which team are you rooting for? I answered "the ones in the red shirts".