How confident is Mel Gibson at this point in his career? Confident enough to send Julia Roberts a freeze-dried rat in a box.

Faithful to his reputation as a prankster, Gibson, 40, recently welcomed his beguiling costar to the Manhattan set of Conspiracy Theory with the doodad, gorgeously gift wrapped but more suited to Stuart Little than Martha Stewart. Such is Gibson’s style, a blend of the courtly and the crackpot. If other ticket-booth stalwarts like Harrison Ford and Tom Hanks provide us with an ideal mold for sturdy, decent, movie-star decorum, then Gibson tosses back the mold with a slight fracture in the porcelain. ”They’re regular guys, but Mel’s a bit more of a time bomb,” says Geoffrey Rush (Shine),who’s known Gibson ever since they shared the stage (and a rented house) during an Australian production of Waiting for Godot in 1979. ”There’s something in there ticking away.”

The past year was explosive for Gibson. He bookended 1996 with conquests both creative and commercial, sweeping the Oscars in the spring with Braveheart, which scored him Best Picture and Best Director trophies, and then plundering the box office in the fall with Ransom, which made $34.2 million its first weekend — the largest live-action three-day opening in Disney’s history.

Not only did Gibson pass these high-pressure milestones, he did so with the same reckless ease that has formed the cornerstone of his big-screen appeal over the course of 17 years. On the frigid set of Ron Howard’s Ransom, he spent most of his downtime cracking wise and playing Scrabble — this despite a gut-churning bout of appendicitis and that potentially head-inflating attack of the Oscars in March. ”It was certainly a kick to get it,” he says of the Academy avalanche, ”but I was dying to get back to work. I mean, otherwise, what do you do? You dust off the mantel.”

Gibson has come off like a charismatic hybrid of Cary Grant and Beavis ever since his early outings with the Mad Max and Lethal Weapon series, but the past year planted that roguish persona firmly in the pantheon of screen idols. And if that persona has caught him some flak from the gay community in the past — an image intensified by Braveheart, in which a gay character was tossed from a window — well, Gibson recently set out to do some shrewd image polishing by agreeing to host a seminar for 10 lesbian and gay filmmakers on the set of Conspiracy Theory.

Gibson’s has always been a package of classic proportions — a matinee idol’s blue eyes, dark mane, and jutting jaw — but this year, more than any other, he proved that there’s more to him than wrapping. Tear open the package and the contents are bound to surprise.

— Jeff Gordinier, with additional reporting by Rebecca Ascher-Walsh