This cutie's name is Marilyn Patch (she changed her last name to Arnone when she married) and she talked about this incident in a latter-day interview. Pretty interesting BTS info on this...
Q: Did any unfortunate or embarrassing mishaps ever occur during taping that didn't end up on the air? I'd love to see a "Howdy Doody" blooper reel.
Marilyn: All the time. So much fun. I'd love to see the blooper reel myself again. This wasn't exactly a blooper because the crew planned this trick on me but for me, it was a blooper because I wasn't expecting what happened...OK, the director, Errol Falcon, and the crew had planned this scene where everyone was getting squirted by Clarabell and they got to me and I said something like "I always like it when somebody else gets squirted by Clarabell!" at which point someone on the catwalk dropped a bucket of water on my head.
Ok, I was expecting that. What I was NOT expecting was that on the heels of the bucket of water dropping on my head, I was pounded with a pie in the face. Now, that expression was priceless! Guess they thought that if I knew it was coming, it wouldn't have looked as funny! Good thing I'm a good sport!