A bearded dragon, in a tank, with fluorescent light left on.
This was the oddest part of it, but in general, they just hadn't moved out.
We owned the ground floor flat and they lived above us in an upper flat over 2 floors. When their property came up for sale, we bought it so we could eventually convert and have the whole house.
As we knew them, my husband said 'don't worry about timings for moving out', meaning that we didn't mind if they weren't quite finished for the midday exchange as long as they were out that afternoon.
Nope. The house was still FULL of their possessions at the end of that day. Washing still over radiators and in the washing machine. Kids schoolwork and laptops, phones, cameras etc all over the kitchen worktops. Couple of mattresses still in the house. Dirty dishes in the sink. Toiletries and towels in the bathrooms.
And the bearded dragon...
It took them a good week or so to collect everything, but we needed to decorate so we could rent it out to pay the mortgage, so we were decorating as they came and went. It was completely bizarre!!