Adding an element of surprise to an event not only engages guests; it also makes events more memorable, and can help cement a brand's image as whimsical and forward-thinking. Here's a look at the ways events—from galas to holiday parties and conferences—have incorporated unexpected elements.

It's typical to use a celebrity as a featured entertainer. But guests are more surprised to encounter celebrities in unexpected place—such as behind the bar. At the MSNBC's White House Correspondents Dinner after-party in Washington in 2012, MSNBC host Rachel Maddow poured drinks for part of the evening.

Planners aimed to incorporate plenty of "surprise and delight" into the Engage Conference, which was held in Orlando in December. One such surprise was announcing to the conference's 350 attendees that they were "going to Disney World" after the second day of programming. Confetti fell, glittery mouse ears were distributed, and Disney characters appeared to amp up the excitement before guests headed to the Magic Kingdom. The 14-piece Main Street Philharmonic Marching Band (pictured) also appeared in the Four Seasons's ballroom as part of the surprise announcement.

Nearly 5,000 fans of fantasy films, TV shows, and books gathered at the Orange County Convention Center in 2014 for LeakyCon, an annual convention. That year, organizers launched “pop-up programming”—nearly two dozen carefully orchestrated occurrences that were not part of the official schedule. One of the pop-up events that generated the most interest from attendees was a reenactment of the final scene from the second season of Sherlock, with actor Maxwell Glick playing the part of Dr. Watson.

For company gatherings in particular, surprises don't have to be limited to the course of a single event. For example, in 2008, Sg2 Health Care Intelligence headed to Chicago's Cafe Brauer for a company party (pictured) that culminated a series of holiday perks. For the week leading up to the event, employees were treated to in-office wine tastings, manicures, and massages.

Another way to surprise guests is to keep them amused and engaged during otherwise tedious parts of an event, such as standing in line to register or waiting for valet. At the Shedd Aquarium's 2008 gala in Chicago, fire dancers from Pyrotechniq performed for guests waiting for their cars after the event. The surprise aligned with the institution's overall brand messaging. “This is something we do at Shedd Aquarium on a daily basis—engage guests while they are waiting for something, to make the time go faster and the wait not seem so long,” said Jennifer Baryl, then the senior director of the aquarium.

Guests always enjoy gifts—perhaps even more so when they're unexpected. Coupa, a spend-management software company, hosts an annual user conference called "Inspire." In 2014, planners from Roar Events surprised guests by sending them home with boxes of doughnuts.