The term "fifty one fifty" derives from California Welfare & Institutions Code section 5150, the provision that allows for a person to be held in involuntary psychiatric lockdown for up to three days if that person is deemed to be a danger to himself or others. It isnow used as slang for crazy, etc.
He's a real fiftyone fifty. Alt: They hauled him in on a fiftyone fifty.
A girl who from a distance of fifty yards away appears to be hot, but as you continue to approach you realize that many features that you could not previously see cause her to be in fact unattractive.
Alex to Jeff as they walk to class: Dude check out that blonde girl up ahead, I'm gonna get her number.
After they walk past without stopping to talk: Ok nevermind she was just a fifty yard fake out.