Here are some of the costume ideas for couples!

James Bond & Bond Girl
Jane Austin & Mr. Darcy
Laurel & Hardy
Lucy & Ricky
Luke Skywalker & Princess Leia
Mae West & WC Fields
Major Nelson & Genie
Mary Ann & Gilligan
Mary Katherine & Marshall Dillon
Neo & Trinity
Queen Amidala & Anakin Skywalker (Darth Vader)
Romeo & Juliet
Rose & Jack (Titanic)
Sandy & Greaser (Danny)
Scarlett & Rhett
Siegfried & Roy
Sherlock Holmes & Watson (or Victorian Lady)
Sonny & Cher
Supremes & Producer
Tarzan & Jane
Three's Company Gang (Jack, Chrissy, Janet)
Thurston Howell & Lovey Howell
Willie Wonka