Why is my chimney so attractive?

Warmth.....then they get overcome by fumes and fall inside...once below the furnace flue they come to again. You need a chimney cap. If you get a racoon stuck in there you can have real problems with fumes in the house.

I've always had screens covering the top inside of the chimney. You need to try that.

Something is not right if animals can get in there. Not sure if you have any choice in using your furnace right now or not, but a restricted chimney/vent can cause carbon monoxide to back up into the home. It is supposed to be varmint-proof for yours and the animals' sake. I'd get someone on it ASAP. The fix is cheap - a few bucks of 1/2" mesh.

Put a screen cover on it

(my photo)

Maybe they just want to live close to you :)

I have a family of rabbits under my deck

At least you didn't find an SW member stuck in there

zoophilia omg.

Well I guess he saw how nice and curvy it was, and decided to visit you. 🙂

I don't know about the squirrel, but it sounds like avian flue