Not for long. Rodents grow quickly and the rat will eventually eat the mouse.
A baby rat is more likely to be a dark colour when it is newborn, but a baby mouse is pink.
Ummm . . . yes, the baby rat is a rat, but maybe you mean what are they called . . . A baby rat is called a puppy or kitten, a female rat is called a doe, and a male rat is called a buck.
That would be the feild mouse.
Generally no. Mice and rats are different species, and natural enimies. It would be instinct for her to kill the mouse. As with all pets, it is possible for her to behave completely different than her breed standard. I suggest putting the mouse in a wire cage and letting the rat come up to check it out. They can smell each other through the bars, and the mouse will be safe. You can judge how she will react to the mouse this way, and decide if you think they will get along.
a cat definatly.
a pouch potato.
The mouse you found could be a baby rat. Rats have a head that is large in proportion to it's body. If you are sure that it is a baby mouse that you found, it could be infected with pin worms.
Not before the rat eats the mouse.
The rat that attacks the "Darling" baby in "The Lady and the Tramp". Ratigan from "The Great Mouse Detective" Remy and his family from the movie "Ratatouille"
I am sure it can happen, probably more so if a mother mouse has babies to protect. However, a rat is a mouse's predator, so to speak, so in most cases, a rat would probably kill a mouse instead.
If your rat needs to be bathed, baby shampoo would be fine.
a mouse