According to buddhist religion - the better you are in the first life, the better you will be in the next life.
It goes like this.
Good people become lucky wealthy humans or princes
Average people become average farmers and merchants
below average people become poor beggars or unlucky people
Pretty bad people become dogs or cats, or that kind of domesticated animal,
BAD people become bad animals like snake or somthing.
So poeple saying you wanna become dogs or cats... go ahead :P