If anything is guaranteed, there are always surprises at Comic-Con.  And many times, it's the unannounced appearance of a major Hollywood movie star.  This year's best kept secret may have arrived on the first day of the convention:  "Alice in Wonderland's" The Mad Hatter himself, Johnny Depp.

The global superstar has never appeared in public at Comic-Con before and showed up at the end of a "Wonderland" segment featuring director and Depp's longtime collaborator Tim Burton.  The crowd roared as Depp walked onstage and the "Pirates of the Caribbean" star appeared to receive a partial standing ovation as camera flashes went off throughout the room.   Depp didn't take questions and seemed a bit overwhelmed by the response, but tried to throw the love to Burton as the screams continued.  

Depp was definitely a surprise as another Disney star, Jim Carrey, had been rumored to be the unexpected participant in the studio's "A Christmas Carol" presentation, but the comedian was nowhere to be found.

This was also Burton's first appearance at the con and he previewed footage from "Wonderland" and he talked about working with Depp to define the look of his character, The Mad Hatter.

"John and I have worked together many times, but he's never done a characer with orange hair.  So, we scalped Carrot Top's and took his hair," Burton jokes. "We picked out every image throughout TV and cinema with red hair and it's quote a disturbing thing."

In some sort of historical footnote, Depp and Burton appeared onstage only hours before "Twilight Saga" superstars Robert Pattinson, Kristen Stewart" and Taylor Lautner, Nicolas Cage (promoting "Kick-Ass") and "Titanic" director James Cameron were expected to grace the Comic-Con faithful with their presence.

Friday will find Cameron Diaz and Denzel Washington making their own Comic-Con debuts.

Look for continuing Comic-Con news as it happens on HitFix.