Michael Jordan, he ain’t.“ER” star George Clooney, who is moonlighting on weekends as the Caped Crusader in “Batman and Robin,” scared the holy bat wits out of Warner Bros. execs on Tuesday when he badly sprained his ankle playing basketball on his lunch break from his hit TV show on the WB lot. The injury threatened to delay the costly bat franchise feature. Clooney, however, was taken immediately to Northridge Hospital for treatment, released, and told he could go back to work. Just no more hoops for the time being. “Batman ,” which also stars Chris O’Donnell, Alicia Silverstone and Arnold Schwarzenegger, is expected to wrap in a few weeks. A Warner spokesman said most of the principal lensing was already in the can.