Peculiar Plurals

If one goose is a goose
and two goose become geese,
then shouldn't one moose,
multiplied, become meese?

If a mouse becomes mice,
and a louse becomes lice,
then why wouldn't grouse,
in a flock, be called grice?

If one ox is an ox,
and two ox become oxen,
then why in the world
don't two fox become foxen?

It's all so confusing!
Someone please explain
why plurals, when we use them,
are not spelled the same!