When the balloons fall from the ceiling they are obviously filled with air. But in the next shot, they are filled with helium because they float.
When the racers are approaching the finish line on the moon, the first shots only depict 3 lanes in which the racers can pull into and claim a spot, but when Zenon approaches, a 4th lane is suddenly depicted as well.
Before Zenon goes out on the moon, her hair is long and has a twist on each side that meet in the middle. When she comes back, her hair looks much shorter and is in many braids. During that day her hairstyle changes at least twice more.
Because the moon is eternally locked with the same side facing the Earth, the Earth stays the same spot at all times in the lunar sky (at least on the near side). Therefore there is no "Earthset".
When Zenon visits the site of the first moon landing, the flag is the only thing there. All of the Apollo missions left the descent stage of the Lunar Excursion Module, which in this case was right next to the flag.
During a close-up on the moon, when Zenon is talking with Selena, the 'sun' being reflected into Zenon's helmet can bee seen as a light prop. In one shot, it is even possible to see the rim of the light.