When Gene Kelly teams with Arthur Freed, Stanley Donen, Betty Comden and Adolph Green, the result is pure movie-musical alchemy: On the Town, Singin' in the Rain and It's Always Fair Weather.Sparkling with wit and exuberant numbers, It's Always Fair Weather centers on three World War II buddies (Kelly, Dan Dailey and Michael Kidd) who vow to reunite for old time's sake in 10 years. They do. And find their friendship has fizzled - until a day of tangling with romance, the fight game, the ad biz and a new medium called TV restores their bond. Highlights include the buddies' high-spirited romp that uses trash-can lids as dancing shoes, elegant Cyd Charisse's k.o. of a routine with brokennosed pugilists, and Kelly's joyful, astonishing tap dance on roller skates. Wow!