I watched FORBIDDEN PLANET recently, for the first time in a long while. You know what? It's an excellent movie. Sure, it's a bit dated now, but it's also over 50 years old. There is so much to like about it regarding acting, score, spfx, and story. If you've never seen it, make an effort.
But wait, there actually is something else besides laudatory comments. I was impressed by the way the film's comedy relief was tied into a key plot element - the exoneration of Robby the Robot as possible culprit of the mysterious happenings. I call this "key" because Robby is a pretty obvious suspect, and logically speaking, there had to be a darn good reason to eliminate him. Otherwise, the rest of the cast either looks like dopes for not considering him, or they waste a lot of screen time chasing down a meaningless rabbit hole. I liked the solution to the problem, since it added extra meaning to the laughs.
I've also decided that the producers WANTED at least part of the audience to jump to the conclusion that Robby was responsible. The film's famous poster art depicts a much more malevolent-looking Robby the Robot than we ultimately got. The trailer, on the other hand, is quite plain that the "something" responsible isn't Robby. That makes it easy to chalk the poster up merely to artistic license.
That was what I'd always thought. Then I watched the special features on the DVD (my last viewing was on VHS in high school!). One of the special features was a pair of clips from the TV series MGM PARADE. Both clips use Walter Pidgeon to promote FORBIDDEN PLANET, but it's the second that is important here. The second clip introduces the audience to Robby the Robot. There's much in the segment that is familiar to anyone who's seen FORBIDDEN PLANET, but there's something different at the end.
Here, watch the clip and see.
OK, what do you make of that? It's a largely innocuous little bit, which even indulges in some tongue-in-cheek fourth wall breaking. Then it takes a downright sinister turn at the end. It seems to be implying something to any viewers of MGM PARADE considering checking out this new picture - Robby the Robot is not to be trusted.
Except, of course, there's nothing even vaguely similar to that in the movie (although it's another story in some later usages of the Robby character). A brilliant example of misdirection? Could be. I'm not familiar enough with the particulars to say for sure. But I'll just bet a lot of people immediately thought to themselves, "Yep, the robot did it," and felt very pleased with their deductive abilities as a result.