Friz Freleng must've been a fan of Robert Louis Stevenson's classic, Dr. Jekyll & Mr. Hyde. How else to explain the fact that Freleng used the book as source material for not one, not two, but three shorts, two of them starring Sylvester.
However, it's Tweety who gets top billing in 1960's "Hyde & Go Tweet", in which Freleng tweaks the traditional story by making the formula so unpredictable that both Dr. Jekyll, who appears briefly, and Tweety, after a dive into the bottle of formula to escape Sylvester, change at inopportune times during the day. None of this is going on at night.
Freleng's other adaptation featured Bugs Bunny, and if we're lucky, we'll see "Hyde & Hare" before this month is out.