That mouse will have a tail (i.e. The thing will have a long train of consequences).
More Dutch Proverbs:
He measures others by his own standard.Dutch
Every bird sings as it is beaked.
Dutch
He cannot lay eggs, but he can cackle.
Dutch
Little things are pretty.
Dutch
He would be wise who knew all things beforehand.
Dutch
Truth is lost with too much debating.
Dutch