Scariest moment on this show!!

False face in the candy machine try watching on a dark stormy night in the dark

Yeah, as a small child I saw the giant clam episode in its original network run. I loved the show, and Robin was my favorite thing about it, so that had me "bouncing off the walls" to see the clam actually swallow him!

And that was the first occasion when, instead of just one day, they were going to make us wait a WEEK to see the resolution! It fits, though, because they would have a one-day cliffhanger every week, where Batman and/or Robin were threatened with death; so for a special week-long 'cliffhanger', it had to be a "cliffhanger among cliffhangers": the apparent successful carrying out of Robin's demise! It worked!
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I totally agree, at least from the perspective of a pre-school age child, which I was when I saw this episode during its original broadcast. I don't remember a lot from that age, but I have vivid memories of the television the family sat down to watch. The very appearance of the giant clam was horrific to me at the time, never mind that only Robin's foot is left out of its mouth!

Making matters worse, although we did tune in to the final episode (I know I saw the famous Penguin/Joker battle in the batcave), we must have missed the opening minutes (and therefore the escape from the clam). Or maybe I couldn't bring myself to watch. All I know is, many years passed before I ever finally saw the scene with Batman breaking his chains and prying open the clam's mouth. So the image of the dark, giant, colorfully lit clam stayed with me for quite a while!

"He likes his tea stirred anti-clockwise..."

Either hanging behind balloons and waiting to be shot with real guns as swapped out by the Joker, or asphyxiation by the Penguin, those were pretty nasty for the day... And, of course, the Mad Hatter's radiation cabinet, if not less realistic, still made an impact - rare for season 2.

The clam terrified me as a kid. I hear the clam was a FOX prop from "Voyage to the Bottom of the Sea". I know FOX used quite a few of the same props on their 60's genre television shows. I know they all employed the same FX company LB Abbott. It must have been FOX's in-house company.