_Monkey Business_ works if, and only if, you can buy the premise that a lab monkey, working behind the scientist's back, can produce an elixer that makes people young again and dump it into the lab's water cooler to watch the results. I find suspending disbelief here no problem, and the result is a wonderfully silly movie. Cary Grant is spot on as the absent-minded scientist, Barnaby Fulton. (The opening credit scene, which seques seamlessly from Cary being referred to as "Mr. Grant" by the off-camera director to Cary being Barnaby Fulton, is a classic in itself.) Ginger Rogers (Mrs. Fulton), is hardly credible as a scientist's wife, but she is brilliant whenever Mrs. Fulton is under the influence of the elixer. Monroe is effortless as the dumb blonde secretary wanting to have "fun" with the youthful version of Barnaby Fulton. Charles Coburn is perfect as the frumpy boss, Mr. Oxley. The comedy is in the situations and dialog that develop as the elixer is repeatedly unwittingly imbibed by Grant and Rogers, and then by others. I would rather not spell these out, but they are fully within the screwball comedy genre that goes back to the 1930's.