not that I am aware of.
you could probably do that with cheat engine, by finding the memory associated with each and replacing the character's with theirs. but the sex animations likely will revert to the player character as I assume for interactive accuracy, they become one sprite during sex. where interactive accuracy means the placement and direction of each sprite being aligned so the dick goes where it's supposed to and he's not humping some girl's thigh, or air humping.
by making them one sprite and merely making the character's graphics invisible and or swapping the monstergirl's graphic to include the character's during sex you eliminate any chance that the player will be off center.
Another way to do it is parenting the player character to the monstergirl and clearing the player character object's parent inverse, then zeroing out the player's location and matching the monstergirl's forward vector. thats alot of steps but it keeps the sprites separate. the problem being you need to mute or disable physics on the player to prevent anything bumping him during the animation.
it's much easier to just lock the player to the monstergirl's location make them invisible and add their graphic to the monstergirl's sex animation.
so I doubt he kept them separate.
