A great double feature to pair with The Princess Bride would be The Adventures of Robin Hood (1938) starring Errol Flynn. Both films have a whimsical, adventurous spirit, and Robin Hood delivers a mix of action and romance with a good dose of humor, much like The Princess Bride. The colorful costumes and swashbuckling scenes are sure to inspire some laughs and excitement. Plus, the chemistry between Flynn as Robin and Olivia de Havilland as Maid Marian brings a delightful romantic thread that'll match the charm of Buttercup and Westley.
Another option could be Stardust (2007). It's a bit more contemporary but shares that fairy tale adventure vibe, packed with humor, magic, and quirky characters. The film's blend of romance and adventure rivals the storytelling style of The Princess Bride, particularly with its charming narrative style and memorable characters like the star (Claire Danes) and the pirate captain (Robert De Niro).
These pairings each bring their unique flavor while remaining in the charming, adventure-filled realm alongside The Princess Bride. Enjoy your movie night!