5. Two of their biggest collaborators are close friends

George Lucas and Steven Spielberg are close friends, having worked together on the Indiana Jones series. Lucas, of course, collaborated with Disney on Star Tours and Captain EO during the mid-1980s.

In Spring 1986, Peter Alexander, a former Disney Imagineer and one-time college roommate of Steven Spielberg, was working on a giant King Kong figure in a soundstage on the lower lot at Universal Studios Hollywood. Spielberg arrived unannounced, and Alexander offered to show him Kong in action. The movie director was suitably impressed, and said: "You guys are pretty good at this. My friend George Lucas told me only Disney could do this. He just took me on Star Tours at Disney. He said, 'You screwed up going with Universal. They could never do a Star Tours'”. In Spielberg’s mind, he was already wondering what Universal’s creative team could do with another science-fiction property, the Back to the Future series.

Ultimately, Spielberg would sign on as a creative consultant with Universal - a lucrative role that he continues to this day. Lucas, meanwhile, eventually sold his production company, Lucasfilm, to Disney for $4 billion.

4. They've both used the same creative talent

One of Universal's most expensive and innovative attractions in the 1990s was Terminator 2 3-D, which combines 3-D on-screen action with live actors and physical effects. The director of the first two Terminator movies, James Cameron, came on board and actually directed the movie sequences, as well as securing the all-star cast. Disney, of course, is now working with Cameron to bring his Avatar movies to life in Pandora - The World of Avatar, due to open at Disney's Animal Kingdom in 2017.

Dozens of former Disney Imagineers have gone on to work for Universal. Thierry Coup, for example, helped design Discoveryland at Disneyland Paris and the park’s unique version of the Space Mountain roller coaster. He moved to Universal Creative, where he played a leading role in the creation of The Amazing Adventures of Spider-Man, Harry Potter and the Forbidden Journey and Transformers: The Ride.

It's not all one-way traffic. Scott Trowbridge, the former vice president of Universal Creative who led the design of much of Islands of Adventure, was hired away by Disney to take the lead at its Imagineering division.

3. There are Disney characters in a Universal theme park

In August 2009, Disney announced that it would acquire Marvel Entertainment in a $4 billion deal, instantly adding 5,000 new characters to its line-up. It was the latest in a string of major acquisitions by new CEO Bob Iger, who had replaced Michael Eisner in 2005.

In a bizarre situation, arch-rival Universal would now be hosting Disney-owned characters. The resort was adamant that it would not be dropping the likes of Spider-Man and the Incredible Hulk any time soon. "Marvel Super Hero Island at Universal's Islands of Adventure and the Marvel characters are a beloved and important part of the Universal Orlando experience. They will remain so," said spokesman Tom Schroder.

2. There is a (former) Universal character in Disney's theme parks

In February 2006, Disney struck a deal with NBC Universal to bring Oswald the Lucky Rabbit back into the Disney fold. In exchange for handing over the Oswald rights, NBC was allowed to hire sportscaster Al Michaels from Disney-owned ABC.

Since then, Oswald has made a number of appearances at Disney's theme parks. He is currently meeting-and-greeting guests at Tokyo DisneySea.

1. Disney turned down the property that revived Universal Orlando

After the huge success of the first few Harry Potter books and movies, it was inevitable that rumors would begin to circulate that theme park operators would seek to license the characters for use in rides and shows. Realistically, only Disney and Universal had the money to do J.K. Rowling's creations justice.

Disney came close to snagging the rights for Potter, getting as far as signing a letter of intent with Rowling. But it walked away when Rowling demanded too much creative control over the project. Universal was only too happy to pick up the pieces - and the hugely impressive Wizarding World of Harry Potter at Islands of Adventure was the result. After struggling through much of the 2000s, Universal Orlando is now riding high under the new ownership of Comcast - and it largely has Disney's decision not to proceed with Rowling to thank for this success.