Delicious, rapid-fire screwball romp. Barbra Streisand (looking radiant) plays a freeloading kook who brings havoc and chaos to everyone in San Francisco. Peter Bogdanovich has directed a true comic gem, with absent-minded professor Ryan O'Neal the perfect foil for Barbra's nuttiness; Madeline Kahn in a fizzy, frantic debut as O'Neal's domineering fiancée; Austin Pendleton terrific as Mr. Larrabee, who spells out fun ("F.U.N."); Kenneth Mars hilarious as O'Neal's primping, preening competitor for the Larrabee Grant. In the days before cable-TV and VHS rentals, "What's Up, Doc?" played theatrically for a couple of years. Obviously in love with classic cinema, Bogdanovich turns out to be a real audience-pleaser of his own; he masterfully sets up gags that might otherwise be corny or familiar and gives them a fresh, groovy spin. ***1/2 from ****