Barney: Ted, do you know how long it takes a woman to decide whether or not she's going to sleep with a guy? 8.3 seconds. After that, her decision is made. She will not change her mind.
Ted: That's ridiculous.
Barney: Is it? Describe your first 8.3 seconds with Stella.
[flashback to Ted in the waiting room:]
Stella: Lower back butterfly tattoo, you're up.
[Ted and a woman stand up at the same time]