The comic tone of Lasse Halstrom’s Casanova (Disney, 12.25) isn’t exactly “farcical,” which, for some of us, means humor that’s cloddishly broad and frequently unfunny. Casanova‘s alchemy is more subtle; it’s selling laughs through the filter of a certain subdued old-world lunacy. It almost feels as if Hallstrom and his cast were on mescaline when they shot it. Does Casanova feel as whimsically stoned as Richard Lester’s The Three Musketeers? Maybe not, but it’s a very close relation. I saw it earlier this week and concluded right afterwards it’s the most satisfying Lasse Hallstrom film since….I was going to say My Life as a Dog but let’s hedge a bit and say What’s Eating Gilbert Grape?. Ledger plays the legendary Venice cocksman with just the right portions of sincerity and insincerity…a very delicate brew. Costars Sienna Miller, Lena Olin and Jeremy Irons more than hold their own, but Oliver Platt gives the biggest standout performance as the pot-bellied Papprizzio. (A friend who just saw it in Sydney told me this morning he felt “more emotionally invested in Platt’s buffoon than Ledger’s Casanova.”) While I’m on the subject, the MPAA’s ratings board has again passed down an idiotic decision in giving this mildy frothy comedy an R rating because of a simulated oral-sex scene. My kids told me three or four years ago that oral sex is a total so-whatter among eighth graders (at the school they were attending in Tiburon, at least) so you’d have to think that kids who are 12 and 13 and 14 thesed days would barely raise an eyebrow at simulated off-screen oral sex in a film. Sorry, parents, but we’re no longer living in a Wonder Years world. A PG-13 would have been more than sufficient.