My Little Pony XLVIII: I say Ol' Chap, how about those Equestrians?

[Kurgan]

Or possibly Starswirl the Bearded, largely because he's been dead for a thousand years.

A Unicorn never arrives late for a date, he always arrives exactly as planned. Besides, the fic can focus around the use of time magic by Starswirl to get all the booty calls. ALL of them. That or maybe breeding with every one of Spitfire's ancestor's to create either a horribly inbred abomination or the next generation of ponykind...for SCIENCE!