This IS my happy face.
I recently moved into a new home, and I must say, it makes all kinds of strange noises at night while I'm trying to sleep. Since cats are nocturnal, I thought maybe you had explored your house at night and could tell me what the strange noises might be.
Perplexed in Princeton
I don't know that I'm actually nocturnal, as I can be hit by a nap attack any time, day or night, but I do know a thing or two about weird sounds, so I'll try my best to help.
If you hear a scratchy scratchy noise, the kitteh has found something it's not supposed to be playing with, like a ponytail holder, and is aggressively swatting at it on the hardwood floor.
A crashing sound means your kitteh was bored and decided to knock something off the table / shelf / counter, where it rightfully belonged. Probably it was made of glass and now you think an axe murderer has shattered your patio door and is making his way toward your room. Just some bonus amusement for your kitteh.
A scrape-y sound means your kitteh has found one of your circular knitting needles and is now dragging it around the house in her mouth, with the metal tip scraping across the floor.
A loud bumping sound means your kitteh decided she needed to scratch her ear while IN the litter box, and her leg is banging repeatedly against the side.
A rustling sound means that kitteh has found her way into the box of tissue paper you keep for gift wrapping, and is now shredding it with her claws.
A crinkly sound means kitteh has found an errant piece of packing tape you didn't pick up and is now chewing on it, because packing tape is inexplicably tasty.
I hope that answers all your noise-related quandaries!
Have a purrrrrfect day!