Difficult question.... !
Our Billie was alone in her cage or run for many years. She always seemed to be a haapy bunnie.
Here she is:


Later we got a guinea pig too. Jasper has his own cage, and it stands next to Billie's one.


Last summer, we put him in the outdoor run too. My hubby made a seperation, so Jasper wouldn't be bothered by Billie.
But..... Billie found a way to get under that seperation fence, and since then..... Billie and Jasper play together and are the greatest friends!!