Frogs. It's not like they're unusual. Back in Murrumbateman we had a dam across the road and summer nights were full of croaking. We even got invaded one night - over 30 little frogs somehow got under the front door and hopped single-mindedly for the kitchen, where we caught them and tossed them out the back.
Occasionally one would just appear inside from somewhere.
Here there are cane toads at night (easily disposed of with a squirt of Dettol), cute green tree frogs that throw themselves at walls and windows with a thump but otherwise don't disturb us,
and then there are these little grey frogs.
They love to get into pipes and gutters and make a big, amplified noise. We know when they're in the toilet cistern because we can hear them at the other end of the house. Pretty good for a creature only a few centimeters in length. Our record for the number in the cistern simultaneously, btw, is 18. Last night there was one in the shower, one the other side of grating, and it was so loud that we couldn't sleep. A mat over the pipe, and two closed doors, were needed to muffle the noise! How do they do it?!