Geckos

For those who have never seen a gecko other than in a Geico ad, here’s one on the wall outside my apartment.

They have feet that adhere to surfaces and can thus climb even smooth surfaces, such as walls. Wikipedia says that they can even walk upside down (e.g., on ceilings), but I haven’t seen that.

Many species are well known for their specialized toe pads that enable them to climb smooth and vertical surfaces, and even cross indoor ceilings …

I have had a few in my apartment (scared the crap out of me the first time it happened), but they mostly stay outside.

Positive: They eat bugs. Negative: For small creatures, they make a hell of a noise.