A year and a half ago, nobody believed the rumors of a possible fourth Indiana Jones installment, 18 years after The Last Crusade premiered. But since the trailer for Indiana Jones and the Kingdom of the Crystal Skull launched last week, we finally believe it.

A lot of crazy secret stuff is going down, causing a lot of speculation. Here are some of the rumors about the new Indy (if you don’t want to know any of the possible secrets, stop reading now):

– Karen Allen, who played Marion Ravenwood in Raiders, is back in the role, and John Hurt might play her father.
– Shia LaBeouf might be Indy and Marion’s son.
– One big sequence might be Indy and Marion’s wedding.
– Cate Blanchett might be a Russian bad-guy and the main villain.
– Indy’s weapon of choice might be a bazooka.
– The treasure of this movie might be an alien object (a crystal skull), so there might be some aliens. Rumors say that the alien dummies from Close Encounters were used on INDY IV’s set.
– Some of the movie may take place in Area-51 (where some believe the Ark is hidden in the end of Raiders).
– There might be some Aztec or Mayan stuff.
– There might be some relics of a supernatural nature.
– There might be a river chase.
– There might be a jungle sword duel.
– There might be giant ants.
– There might be a location called the Temple of Akator.
– There might be yet another Indiana Jones trilogy after Kingdom of the Crystal SkullL. Word has it that LaBeouf has signed on for a total of four Indy movies, the next three revolving around his character.
– And the big one: The Kingdom of the Crystal Skull might revolve around many events from Raiders of the Lost Ark, including the Ark itself. Some speculators have come to this conclusion after set photos leaked online that appeared to be the warehouse where they stored the Ark. The belief is that The Kingdom of the Crystal Skull will come full-circle with Raiders to give complete closure to all Indy fans.

Indiana Jones and the Kingdom of the Crystal Skull is set for a May 22, 2008 release, and if you haven’t seen the trailer, you can check it out at IndianaJones.com or movies.yahoo.com.