Kitty!

[Lukeje]

Cats can reach terminal velocity you know.

Supposedly they don't if thrown above any floor higher than the 7th because they can use the skin under their arms to slow themselves down (like a parachute). Though it all sounds like urban-legend to me...

Yeah, no, that's bullshit.

There's mention of it here [http://en.wikipedia.org/wiki/Cat_righting_reflex], though it does also contain a more likely explanation;

...that upon an excess of seven stories the cats experience a higher fatality rate which precludes the owner from bringing them in for medical attention.

 

[MelziGurl]

If the neighbours cat is a male, that could be your first problem. Although it's odd that it just wanders into another house like that.

 

[BonsaiK]

There is a type of cat door that you can buy where you get your cat to wear an electromangetic collar which triggers a latch inside the door, thus only allowing your cat into the house and not any strays. Inquire at your local pet shop, they will have them.