How to Potty Train an 18-Month-Old

So do you want to know the quickest, fastest way to potty train a one-year-old from diapers to underpants in just one weekend?

Yeah, so do I.
But apparently, it's happened!

Yeah, sometimes she wears clothes.  (But not often!)

We stumbled into potty training completely by accident one evening back in October.  Elsa stood watching the tub fill for a bath, and something about the look on her face made me think she had to pee.  I swooped her onto the potty (we have one with a child's seat attatched to the lid - it's amazing!).  And she went!

Several hours later at bedtime, she was still dry, so I set her on the toilet again.  And she went again!
And that was really all it took for her.  I don't know how or why it was so easy, but it was.  After a month of disbelief with only maybe one accident a week, we started putting her in underpants for church and short trips to town.  Now two months in, I feel fairly confident that she will stay dry, even when we're gone all day.  The only accidents we've had are when I've forgotten the fold up potty seat (she won't go on a regular seat, even if I hold her) or when a certain aunt takes her to Sonic and loads her up on Sprite.
All the kids have started potty training young, but she definitely gets the award for 0 to 100 in the shortest amount of time.  I don't think it has anything to do with my parenting skills (you'd think I'd have learned something by #5!), but more so just that I happened to catch them when they were curious and when I had the time to work with them.
Potty training one so young has it's disadvantages - she doesn't talk much yet, but she's figured out "GO!" will get an immediate response.  I'll be sitting on the couch and she comes and gets me with a "GO!"..........and then leads me to the snack cupboard.  A couple times I've just taken her to to the bathroom, and she will start yelling at me from another room.  I ignore her, because I know she's just went - only to find out that pee wasn't all she had to do....  Also, since she's so little, there's no way she can take herself to the bathroom.  She can't climb up onto and turn around without falling in, so it's 100% parent-assisted.
But still - a small trade for not having to change poopy diapers any more!!!