Which AUs Are Most Popular?

As I’m sure you’re aware, there are a LOT of AUs. Some of them very similar to the original, others, completely different.

What I’m wondering is, which are the most popular?

What I’d like you to do, is tell me in the comments what your favourite AU is. If it has already been said, like the comment to get it to the top. After a week (on the 25th) I’ll make a poll with the top five.

Whichever AU wins the poll will be declared the (very unofficial) Most Popular AU!