Okay watch, probably won't watch again, and can't recommend.
It was interesting to see a young Jodie Foster...
While I appreciate this popularizing (I'm still not convinced it birthed) a trope of "body swapping", it seems very uninspired: as if they said, "Wouldn't it be great if a kid and a parent swapped?" and then just stopped coming up with ideas. It was honestly very jarring on both swaps, the latter being honestly confusing (despite having addressed it directly).
The movie made me realize how difficult it would be to swap places and attempt to "be" that person without a shred of preparation. I'm sure that's a bad sign as I should be more entertained by the novelty or adversity of the situation, but no.
It's not that its a bad movie, there's a lot going on, a lot of it decent, but it's very dated. Even the action in it is a little awkward, but I certainly see why people in 1976 would have been impressed with this.
On the other hand, I don't imagine people were talking about it for very long. There is a lot of thought narration that occurs, which isn't very engaging, and most of the engaging humor is cheap physical humor of "what's going to go wrong this time" so you're not engaged very long and the impression doesn't hold.
The part of the movie that is actually rather good is the substance of teaching everyone to appreciate everyone else in the family, but we really took "walk a mile in his shoes" to an extreme here. There are more palatable ways to express the concept, and more movies that use this trope.
I honestly suggest the 2003 version over this one, it's just not very memorable.