How 65 people managed to keep this thing a secret, I don't know, but when the bride shows up at the shower wearing a bathing suit and basketball shorts, you know it was a surprise.
I'll talk more about the shower shortly, including some of the really fun games, but a few tips on having a surprise shower for somebody:
1) Have clothes for them to change into and if they have unruly hair, bring a brush, bobby pins, and a straightener. Don't forget to bring a bra/undergarments that will go with the clothes/dress though, in case the bride shows up in a swimsuit.
2) If anyone is coming in from out of town, don't tell the bride/guest of honor - it will tip them off immediately. L. was pretty sure that the shower would be last weekend until we left on Saturday. Thankfully, we thought of that plan and it was enough to throw her off.
3) Have the shower early - the wedding is still more than two months away, but if it was later, she would have been expecting it every weekend, since she knew it was a surprise.
4) Put Surprise in big letters on the invitation and make sure everybody knows it was a surprise.
5) Have the excuse that gets the guest of honor there be a spontaneous one - L. had plans with her roommate to spend the whole day with her (to make sure she had no other plans) but then at the last minute her roommate got "run off the road" conveniently at the Elks Lodge where the party was.
6) Have a plan in place of things for people to do while they wait for the bride/guest of honor to get presentable - everyone filled out their bingo cards for the gift-opening bingo, and the bridesmaids all started in on the wine, since they were finally able to relax.
I will admit, I was dubious and very stressed out about the surprise shower. I was nervous all morning and all of the bridesmaids were extremely tense to make sure that everything went off without a hitch, but everything worked perfectly and L. was either really surprised, or did an excellent job of faking it.