this is tagged with gay but how can we be sure such a concept really exist among aliens?
Notice how skinny aliens usually are when depicted? I think when it's time for them to reproduce they have a great big starcraft tournament (they probably play protoss, fucking hubris) and the winner, even if it's a filthy macro player, gets selected to partake in a great big gigantic mukbang until they're so obese they explode and tiny little baby aliens rain down from the sky.