a diffrent kettle of fish
a whole new bunch of trouble you didn’t ask for
You thought you had one problem. Now you’ve got one problem, another problem, and a problem that involves your cat being a detective.
You thought you were going to sleep. Now you’re going to sleep, but your brother is also going to sleep and he’s bringing his pet snake.
You had a normal day. Now you’ve got a normal day, a weird day, and a day that involves your teacher turning into a robot.