Triploidy
I was just researching the evolutionary advantages between haploidy and diploidy. In the process I found a very amusing abstract.
From: The evolutionary advantage of diploid sex by A.O. Sousa, et al
We modify the Penna Model for biological aging, which is based on the mutation-accumulation theory, in order to verify if there would be any evolutionary advantage of triploid over diploid organisms. We show that this is not the case, and that usual sex is always better than that involving three individuals.