The moon is also absolutely gargantuan by moon standards. It isn't the largest moon in the solar system, but it is BY FAR the largest in comparison with its planet. Ganymede is the largest satellite of Jupiter and the largest moon in the solar system. Its diameter is only about 3.8% of Jupiter's. Titan's radius is 4.4% of Saturn's. Callisto and Io are the next largest in the neighborhood, with 3.4% and 2.6% the diameter of Jupiter respectively.
Our moon is number 5. It is smaller in direct comparison to the above moons. The diameter of the moon is 3475 km. That is a full 27% of the diameter of the Earth. More than a quarter. That's ridiculous. It's unheard of. The universe is large enough that the word unique probably doesn't mean a lot, but this might be about as close as you get.
This has had a huge impact on our planet. Other things aliens might not have are significant tides. One of Mars's dumpy little potatoes wouldn't be able to move oceans the way our moon does.
Our moon has also stabilized our axis to a massive degree. Without her up there our axis would wobble all over the place and our climate would be far more chaotic. Aliens might not be quite so lucky.
I guess what I am really trying to say is that the moon is extremely cool. I like the moon.