What is the difference in cats of an altered male and unaltered female?

Answer:

Whether a female is spayed or not isnt' visible once the incision heals.

A non-neutered male will have large testicles, and a neutered male will have small, fuzzy sacs where the testicles were before removal.

You can tell a fixed male from a female because a female cat's rear will just be the anus, whereas the male still has a scrotum and penis which look like fuzzy little balls below the anus.

I'm not sure where you'd find pictures of this, but it's really easy to see.
First answer by ID2341378689. Last edit by Nevwyn. Contributor trust: 7 [recommend contributor recommended]. Question popularity: 4 [recommend question].