I would classify it as strange, exciting, mystical and weird that although I can be out at a club with a perfectly attractive woman in the prime of her life, tarted up in her best little black dress, with her darting her eyes at me and occasionally touching me on my knees and shoulders while smiling, I sometimes feel nothing more than a bit flattered, while there are times when a semi-dumpy grandmother in her mid-sixties who works behind the deli counter will make eye contact with me while slicing ham in her hairnet and plastic gloves, and something inside my psyche says "this one".
This is just a single example. You can substitute "schoolteacher in mom jeans who should probably get her hair done and lose about 20 lbs" or "Wal-Mart cashier with weird glasses and a bit of acne" or myriad other things for the hairnet lady. There appears to be no pattern that would support the declaration of a preference based on any set of characteristics. It's not too common, but not uncommon enough for me to be upset about it any more. Most of the time I know exactly why I'm attracted to a woman and don't feel a need to analyze it. Other times it's, like "What the hell is going on inside my head?"
Ever feel that way?