Tie a leash around its neck and yank it back. If it is burning, smoking, disintegrated (i.e. no animal just the collar), gasping for breath, or the like, I’m not going. Of course the danger in yanking it back is that it might Bring Something With It.
I’ve been thinking about this - it boils down to whether maggenkid is with me, after all, I’m a mother first.
So, if I’m on my own… I carry on with my day.
If she’s with me, we grin at each other and *run *through the door.
I’d open the door, then peek inside. If I don’t see anything dangerous or threatening, I go in.
I’d drop something small like a pen in, to make sure there was a floor on the other side, then go through. Maybe it’s a door to another world…or maybe it’s finally the proof that the afterlife or God exists or something else amazing like that. As a lover of knowledge and proof, I would have to know. 
I wait for the countdown. When it hits “1”, I step in.
'Cos, I think it might be an elevator. But if it’s not, then I’ll still get inside. 
Grey mist.
No sound.
And unless you are The Batman, you are not carrying a small mammal and a piece of rope or string.
I think I’d have to step through because I’d be afraid the door would vanish after the countdown and I’d spend the rest of my life wondering what would of happened if I stepped thorugh.
Well, poop. How am I supposed to know I’m not stepping into a bottomless pit or some celestial elevator shaft? 
I’d feel around with my foot first to make sure there is a floor, but I’d go through (before the countdown is over, 'cause I’m guessing the door disappears after 1). If something like that happened I’d assume I was dreaming or hallucinating anyway, so why not? And I’d never forgive myself if the door went away and I didn’t find out what was behind it.
I’d let it go.
Yes I’d always wonder what was on the other side, but one look at my son would tell me whether I’d made the right choice. He’s enough of the unknown wonders of the universe for me.
Since I don’t have children, or common sense, I’d go through.
(I mean, seriously. If I didn’t, I’d always be wondering what it was all about.)
You’re presumably never heard of the Boomerang Shrew or the Yo-Yo Vole - in which case any ordinary small mammal tied securely to an elastic thread would suffice.
I honestly don’t know whether I’d step through or not. The grey mist doesn’t sound particularly inviting though.
I’m another person with no kids so I’d go through. Heck, it can’t be worse than what’s on this side.
I agree with the others who’ve been pointing out that anyone who can make a door materialize in front of me doesn’t need elaborate traps to do me ill. And I’d go nuts if I didn’t take the chance.
Well, further nuts.
Yeah, but anyone powerful enough to do it, but careless enough to make the intent so completely ambiguous might be better steered clear of.
Well, I’m a person with three small children, I’m my parents’ only child, and I like my life quite well the way it is, so I’m sure as heck not stepping through some mysterious misty doorway.
For one, if they REALLY want me to cross, they’ll come back more than once.
For another, my first instinct for any strange doorway is, it’s probably some kind of trap. Never mind one that appears from nowhere with a bizarre hook to it. Even if there were no mist, and I could see a green field with bunnies hopping around or something on the other side. Who’s to say they aren’t killer rabbits?
In fact my immediate reaction would be to do a 180 and look behind me. If I were setting a trap involving teleporting doorways, I’d pop up two of them on either side of someone, so that in the act of fleeing in a panic from the one in front the person ends up going right through the one behind them.
Put me in another situation, though, where I have really nothing to leave behind worth worrying about, like if I were terminally ill, and I’d step through in a heartbeat.
I’d definitely throw something through the doorway, though. Whatever loose change is in my pocket, or else one of my house keys or a random plastic membership card I have in my wallet.
Very likely. I didn’t say I thought it was a good plan. Just that my curiosity bump is such that it would never leave me in peace passing that up.
And, well, a lot of the reasons that people are mentioning for not going through just don’t apply to me.
I’m no one’s lab rat, thank you very much.
I bet you’d be a lab rat if it was a test to see whether Jessica Alba or Scarlett Johansson was better in bed.
I’m quite suprised at the number of people who would step through. I suspect this number would be decimated if the situation actually occurred! I’m a gambler, but my reaction was more like Q.E.D.'s. I have a strong survival instinct.