Be careful mentioning any animals, actual or fictional, in this place. They become supporting characters and avatars.
What I'm really looking for in this thread are actual expressions that you or your family has "customized".
For example, "the grass is always greener on the other side of the fence". My dad had a neighbor fanatical about having the "best lawn". (Yes, we're Texans.) This neighbor would actually spread manure to feed his lawn. So the expression became:
"The grass is always greener but at least we don't smell like sh.."