The more you search on this topic, the more great ideas you are going to find. Get a bag, purse, backpack, or whatever suits your need. Stuff it full of all the crazy stuff the bride might need. Label it "property of the bride," or something along those lines. Put someone in charge of the Bride Emergency Kit. (BEK)
Whoever is in charge of the bag brings it to the wedding and the reception. They will be seated moments before the "music change" when the bridal party comes in. (Someone you'll put in the front row by the parents is an ideal choice.) The person will tag along for pictures, even if they aren't in them. The person is the last to sit before the party officially enters the reception. You might have this "BEK" person leave the bag in the bathroom at that point.
What are the basics of this kit? Whatever you normally carry in your purse, plus whatever you might need on this day. Your medicine cabinet of usual remedies, make-up for touching up, tissues, extra stockings (if you're wearing them), ballet slippers for the reception, phone charger, chalk to cover any stains on the fly, scotch tape, duct tape, packing tape, a lighter, a bottle of water, your favorite snack bar/ nuts/ non-messy treat, the numbers of every business you've used for the event, a spare house key, safety pins, etc.
Play the "what would you do if" game. Watch the wedding fail videos and see how many of those terror-comedies could be avoided with some planning.
And to you guys out there, a Groom Emergency Kit can be a real lifesaver. What item could you forget that someone will give you a hard time about forgetting? Pin a list to the GEK and get your most reliable bro to make sure you have that stuff.
Tomorrow I'll talk about transportation.