Mark: so what's with that girl Donna you've dated last night?
Barney: Man she playing ping pong on that hot crazy scale! she gave me head under the table then stabbed me with a fork.
The scale is a scale is with the vertical axis labeled "HOT" and the horizontal axis labeled "CRAZY."
A girl is allowed to be crazy, as long as she is equally hot.
If shes crazy she has to be hot, if shes really crazy she has to be really hot.
As long as a girl is above the “Vickie Mendoza Diagonal” she is approved for dating. Vickie Mendoza, a girl Barney Stinson from How I Met Your Mother dated, she played jump rope with that line. This diagonal is a reference to the Mendoza Line in Baseball.
If a female becomes to crazy without becoming hotter, she may drift extremely close to the Shelly Galezby Zone.
Barney: I should give her a call
Devin: So what's up with you and Becca?
Adam: Well, I've been trying to hit it but she keeps drifting across the Mendoza Diagonal. She is getting extremely close to the Shelly Galezby Zone on the Hot-Crazy Scale.