Threat-Level: Killer Tadpole   Gross-out horror is never far
from comedy and The Host, Bong Joon-ho's giddy creature feature,
has an anarchic mess factor worthy of a pile of old Mad
magazines. A broadly played clown show full of lowbrow antics,
Bong's big splat is itself a sort of monster—the top grossing
movie in South Korean history—and, since it surfaced at Cannes
last May, festival audiences having been slurping it down like
ramen.   Bong's allegory is deliberately free-floating; still,
that the thing has its origins in American stupidity and hubris
is made clear in The Host's prologue, set in a morgue on a U.S.
Army base. Offended by the dust on some unused bottles of
formaldehyde, an overbearing American officer orders a hapless
Mr. Kim to dump gallons of toxic chemicals down the drain and
into the Han River. A few years pass and two fishermen spot
something gross swimming in the murk. . . . Cut to the wacky
dysfunctional family who operate a riverside fast-food stand.
Look out! There's an American dir