My auntie the other night was commenting on a film she saw ages ago, the plot of which went roughly along the lines of an astronaut crash landing on a planet which is exactly like earth, although something about it isn’t right, and the only way he figures out that it isn’t earth is that it has two moons.
Does this ring a bell for anyone? She didn’t believe that the SDMB would help me find the answer, so help to prove her wrong 
Um…was it just like Earth except eveyone was was an advanced Ape-man?
Is writing on the planet reversed?
Sounds like “Journey to the Far Side of the Sun,” also known as “Doppelganger.”
Excellent, pinkfreud, that seems to be the one I knew the folks here wouldn’t let me down.
And Dooku, that was my first thought when she described it to me too, but she said that it wasn’t POTA or any variation on that - I probably should have put that in the OP.
I’ve seen “Journey to the Far Side of the Sun,” several times I never recalled seeing two moons.
However, there was a TV movie called “The Stranger” which had a similar plot. I’ve never seen that one, but it’s possible that it had multiple moons.
But just because I don’t recall seeing two moons doesn’t mean that there weren’t. It has been a few years since the last time.
It had three moons, FTR. It was also seen as “Stranded in Space” on MST3K.