[Updated: According to Todd Phillips, via E! Online, Mel Gibson will not be appearing in The Hangover 2. Scroll down for the official update.]

So far it’s been hard to tell what is true or not when it comes to The Hangover 2. From the early “Will they or won’t they return?” rumors about the cast to the confirmed/denied/re-confirmed news of a Thailand setting, what should be a transparent sequel has been weirdly sensational.

Today, we have new set photos of all four Hangover stars back at work on the sequel and a new rumor that a new controversial celebrity will be making an appearance in The Hangover 2.

Those who saw The Hangover know that one of the film’s gret highlights was having former boxing superstar (and frequent tabloid sensation) Mike Tyson make a cameo appearance. Tyson’s scenes were brief, but great, and were filled with winking references to the former Heavyweight Champion’s real-life troubles.

Well, according to the New York Post, Mel Gibson – who has been the center of multiple scandals in the last few years – will be making an appearance in The Hangover 2 as a Bangkok tattoo artist. As you can probably already tell, the joke potential for such a scenario is off the scale.

Here’s what a source had to say about the matter:

“It’s a done deal. Mel will make a cameo as a tattoo artist. Filming is taking place on the Warner Bros. lot, where a Bangkok set has been built, and Mel is expected to film his role in two weeks. Then the production moves to Thailand at the end of October.”

For now take this as a big RUMOR, but personally, I would love to see Gibson onscreen humbling himself by cracking jokes about his own recent (and very public) missteps. A self-referential cameo worked well for helping Tyson step back into the limelight in a positive way, and as I said up above, the jokes pretty much write themselves when you think about “Crazy Mel” as a Bangkok tattoo artist. Fingers crossed that this turns out to be true.

Finally, here are some set photos from the The Hangover 2 that were captured last week, courtesy of Pop Sugar. As you can see, all four guys – Bradley Cooper, Zach Galifianakis, Ed Helms and Justin Bartha – are back in action:

Head over to Pop Sugar for more of the set photos.

Update: Director Todd Phillips spoke with E! Online, lamenting that Mel Gibson will not be in The Hangover 2, afterall:

“I thought Mel would have been great in the movie and I had the full backing of Jeff Robinov and his team. But I realize filmmaking is a collaborative effort, and this decision ultimately did not have the full support of my entire cast and crew.”

The Hangover 2 is currently slated for release on May 26, 2011.

Sources: New York Post & Pop Sugar via Coming Soon