MICKEY ROONEY... What can you say about a living legend? In his bio for SUGAR BABIES he summed things up by writing: "MICKEY ROONEY... formerly Andy Hardy... formerly Mickey McGuire... formerly Joe Yule, Jr."      Still in his teens, his "Puck" in an early MIDSUMMER NIGHT'S DREAM displayed limitless potential.  In a career that has spanned almost his entire lifetime, Mickey Rooney has proven himself one of the most accomplished entertainers we have known.  There certainly is no denying his acting ability.  He is equally adept at bringing a lump to our throats as he is in creating a smile on our lips.  And, of course, there is his musical talent... singer, dancer, and musician (Mickey plays a mean set of drums).      Even though he was born in Brooklyn, one would never know it, since Mickey traveled the vaudeville circuits with his parents and he appeared on soundstages from the time he was a tot.      Touching portrayals in movies such as BOYSTOWN, and THE HUMAN COMEDY, plus the lively musicals in which he appeared with Judy Garland, made Mickey a favorite with the public.  His popularity elevated Mickey to a top boxoffice attraction for many years.  Without doubt, Mickey was one of the reasons Leo the lion roared with pride.      He has been alternating between the stage and television of late and his moving performance in the title role of the biographical BILL yielded him an Emmy Award.  Twice the Oscars acknowledged Mickey, in '39 for personification of youth, and later, in '82, a Lifetime Achievement Award.