"Well... some fillys pride themselves on how much of a stallions, mmph, phallus they can take into their bodies. Some mares are more well endowed in that area than others, you see; given how stallions usually can't seat themselves fully within a mare," Rarity explained. 'At least I don't have that problem with him!' She mentally sang and grinned proudly as she hugged herself tighter against her stallion. 