This mainly applies to males, but there's some stuff that can apply to the ladies too.
1. You're invited to a fancy dress party, and instead of dressing as a valiant Prince Charming, you'll dress up in a skirt and tights, declaring yourself as a fairy, 'just for the laughs'.
2. You're house is lit up like a Christmas tree every single night of the year. And often throughout the day.
3. You'll start singing in the shower, but not normal songs - cheesey musical stuff, or 'It's Raining Men'.
4. You'll make some comment on the opposite sex. Not about their nice legs or hot tan, but about their FABulous dress sense.
5. You'll put on bright blue nail varnish and claim that it's to stop you biting them.