… you wake up in the morning and the song running through your head is “Rio” by Duran Duran.
Seriously.
… Getting ready to crash after an all-nighter you now have “rio” looping in your mind cause you just had to check in one more time.
Thank you twickster.
Best way to get rid of an earworm is to give it to someone else. 
The funny thing about spending time on the dope, and getting to know all these posters from all these other countries, and learning about their points of view, is that you finally realize that…
…it’s a small world after all.
You know you’re a Doper when you see pure evil … and it makes you laugh.
Then it makes you want to kill.
Or when you’re reading a book, as I was, and it just happens to have a character named Opal, which it did, and inevitably that Opal gets introduced to someone else, and in the course of that introduction the other person says, “Hi, Opal”… and you think it’s hysterical.
I need to get a life.
…you are out doing your day to day thang, something gets your goat, and you begin composing a Pit thread in your head.
You get called names and it makes you feel “special”…
But I wouldn’t want to paint it.
Or carpet it.
Or have that tune running through your head.
“Dear Pit; You wouldn’t BELIEVE what happened to me today! I always thought all those Pit threads were just made up, but then it happened to me!..”
Or you spend far too much time thinking about something going on onboard and trying to compose just the right response to it.
I mentioned this before, but I saw an attractive girl, and my first thought was wondering how Dopers would rate her. I remembered a thread we’d had saying that the person taking the photo had the rights to it, not the person being photographed, but I still couldn’t bring myself to do it.
You have a favorite web site, but you never mention it to most people at work. Most people would not fit in here.
Heck, you don’t mention it to anyone save a special few (such as a significant other that is sick of you always starting sentences with "I was reading on the SDMB today…).
Brendon Small
Or, even you have no intention of starting a thread about a subject, the way you think about/through the incident/problem to yourself is colored by “WWTDS” (What would the Dope say).
… you signed up for an account on the straight dope message board.
You stop into an opinion thread to make this brilliant statement: If you don’t like it, don’t <watch><read><eat> it. Problem solved!
You hear what sounds like big news on teevee or the radio, and the first place you go is not cnn.com, but here.