The Bachelor and the Bobby-Soxer (1947)

Teenaged Susan Turner, with a severe crush on playboy artist Richard Nugent, sneaks into his apartment to model for him and is found there by her sister Judge Margaret Turner. Threatened with jail, Nugent agrees to date Susan until the crush abates. He counters Susan's comic false sophistication by even more comic put-on teenage mannerisms, with a slapstick climax.