Which character has the most interesting backstory?

And by that I mean the history of the Social Group before TBBT. Leonard had a cold mother, Raj lived in India, Howard was doted on by his mother while abandoned by his father, Sheldon has an entire prequel series to himself that negates the need for explanation, Penny was from Nebraska and was a reckless, promiscuous student, Amy was lonely and had an overprotective, overbearing mother and Bernadette had seven brothers, an overworked mother and often participated in beauty pageants.

Of all their histories and backstories, whose was the most intriguing, entertaining and interesting in general?

I'm inclined to choose Leonard's, Amy's or Bernadette's. Theirs seem the most exaggerated or intriguing. But of the three, I have to pick Bernadette's.