A woman goes into the doctor because she's missed a couple of periods and takes a test, revealing she's pregnant. So she goes into the doctor to confirm the results, and finds out she's about 3 1/2 months pregnant.

"Hmmmm." she says.

"Is this not good news?" he says to her.

"No, not necessarily. The problem is that I've been with 5 different guys in the past 4 months, I have no idea who the father could be!"

"Well, it looks as though you may want to contact each of them and have them come in for DNA testing. Then you'll know for sure." Said the Doc.

"I can't do that." She says.

"Why not?" The Doctor replies.

"Because, they've changed their Screen Names!"