Planning a 25th wedding anniversary is an exciting task. A 25th (silver) wedding anniversary is an occasion that any couple should be proud of, and deserves to be celebrated in style.
A really fun way to celebrate a couple's life together is to throw a themed costume party that celebrates a passion that they share. A couple that would be interested in doing something like this is probably a couple with a great sense of humor and a lot of love for each other, which will make the event a joy for everyone who attends.
If the couple has a love of period films, throw a costume ball worthy of Marie Antoinette. If they're medieval era fanatics, throw a renaissance fair-style party. Science fiction buffs could throw a party straight out of the bar scenes from Star Wars, or Star Trek, The Next Generation. The reason this idea will hit it out of the park is because it can be executed with either a big or a small budget, and it gives everyone a chance to wear costumes, let their guards down, and show that even after 25 years of marriage, this husband and wife still truly and deeply enjoy each other's company.
Have the invites sent out in a manner that works with the theme. A renaissance fair invite is begging to be sent out on scrolled paper. It would be almost criminal not to record a Jetsons-style video invitation for sci-fi buffs. A really special touch would be to invite as many people from the original wedding as you can.
This fun atmosphere would also be a great opportunity to for the couple to renew their vows. The great thing about vow renewals is that anything goes. They're really an opportunity for the couple to re-dedicate themselves to each other.
Of course, this type of party demands that you serve food related to the theme. Who would be able to resist "Double Chocolate Space Balls" at a sci-fi party?
Finally, record and photograph the event so that the pictures can be put up at the couple's 50th wedding anniversary party.