In the 1990s in the UK, it was gay to wear a backpack using both shoulder straps (as opposed to using one strap over one shoulder, which was the heterosexual way to carry things to school).
According to the best school playground scientists of the time, opening a packet of crisps upside down (i.e. so the branding/writing is upside down, and you open the bottom of the packet, at the top) actually "made you gay".
It wasn't just gay if you did it, but it would literally cause a spontaneous eruption of gayness in whoever did it - who would be permanently gay from that point onwards.