Notes: I've kept rats as pets, and one thing they do when they're chilling out is they grind their teeth and make this "brux brux brux" noise. While they're doing this, their eyeballs pop in and out in a very disturbing fashion. The first time I witnessed this it freaked me out, as I was sure my rat's eyes were about to come out altogether and I really wasn't sure how I was going to get them back in. But no, it's just something they do, and you get used to it after awhile.