If you have a mustache and you hit your forehead on the moon, you’re probably going to break a bone. Ok, so it doesn’t matter so much if you have a mustache, but if you’re travelling fast enough to make it to the moon, you’re definitely breaking a bone if you run into it.
Outer space is cold, and if you're traveling to the moon, you're going to need a lot of coats (こつ). All of these coats will keep you warm, even if you do end up breaking your forehead bone.
Currently there are no similar looking kanji which exist in the WaniKani learning system