Archer had a rather... erm... explosive entrance to the mansion, when he crashed down in an escape pod a mere 300 yards from the mansion.
Archer is not a pony, not technically. He is an alien, from the planet of Novus. Noverians are different in several ways from Equestrians. First and foremost, their size. Archer stands at a monstrous eight feet (2.43 meters) tall when in his armor, and seven feet six inches (2.28 meters) when independent of his armor. The second biggest difference is that Noverians are omnivores, Archer boasts a set of long canine teeth with which he can bite and tear flesh, and he is capable of eating it raw, though he chooses not to. The final difference is that Archer's cutie mark is not at all indicative of his abilities. Noverian cutie marks are representative of their true names, and they are earned when a Noverian foal discovers that name. Archer discovered his name during a meteor shower, when he noticed that the meteors looked like a volley of flaming arrows, hence the name of Archer. Castellus is his family name.
Archer was the captain of a Noverian mercenary crew, but he found himself on Equestria after his ship was beset by superior forces and he was forced to eject in an effort to survive to someday exact revenge for himself and his dead crew. For the meantime though, he will have to live on this planet, which he knows as Solara, until he can find a suitable crew and ship.