Come on! This is one of those stories that has a germ of truth, but in no way is appropriate for the majority. Yes, there have been some people who have been horny and stupid enough to do things like this. Seriously, we're all kind of fucked up - aren't we? But those gay or straight men or women who have been demented enough to shove a pour lubricated gerbil up their ass are far and few between. Just like people who like fucking door knobs or any one of a million different fetishes on the serious fringe.
As a caution - before you do anything like this - ask yourself the reason why? Are you demented? Did your Dad look like a gerbil and you want to make up for lost relationship? Are you just that fucking strange or bored?
I have found in my own sexuality, that I am certainly weird. But that doesn't mean that it's all good. Some things are simply unhealthy and we do them because we want to (against our best interests). I really believe that sticking any small animal up your ass qualifies.