Before putting it in the toaster? Upright toaster.
That’s about it…
No, because the butter will melt and drip down into the bottom of the toaster, and will possibly short out the wires, and definitely create a greasy mess.
I sure wouldn’t. It’s a pretty sure bet that as the butter melts, some of it will drip down into the toaster, causing at least a mess, and possibly damage.
No, but doing it in the broiler or a toaster oven makes it delish!
Instead use the broiler on your oven (keep a close watch since fires can start that way) or even better yet buy a toaster oven which is designed for this very purpose.
No. do it and you will get you little ass whooped. At least that was my experience in the matter. 
Well, butter is flammable because it’s mostly made of fat. Not only might you set your toaster on fire, but you could also ruin the toast, thus, defeating your purpose of saving time. Get a toaster oven or be patient and wait the three minutes.
Clearly someone would make a killing if they’d invent vertical butter.
Only if you put the toaster horizontal.
Where I work, we always LIGHTLY butter the bread before putting it in the toaster for sandwiches. I’ve never had a problem with the toast burning or the butter dripping and causing a mess. I can see how it may happen if you really load the butter on, though.
IME (and I’ve taken apart a decent number of toasters) it’s unlikely that wires will be located underneath the toast. But the chance of a mess is indeed significant.
Why not butter the toast as it emerges from the toaster - when it’s hot and eager to melt butter?
And that’s the thing: why WOULD you do this? A toaster is for toasting; it makes the bread brown, crispy, and delicious. The butter would prevent that, and you’d end up with, at best, hot wet bread.
I don’t know where you’d get that idea. We’re talking about butter, not ice.
Butter browns very nicely. Buttered bread browns differently than un-buttered bread. Grilled cheese sandwiches testify to this.
And buttering after the fact gives a different effect than buttering before toasting.
That said, I wouldn’t want the mess caused by butter melting off a vertical piece of bread in a normal pop toaster. If nothing else, it’d remain in the bottom of the toaster, becoming more rank and burnt as time goes on; I’m sure those fumes would not be appreciated on subsequent toastings.
I know from first-hand experience when I was a kid that if you put gobs of butter on bread (as any 10 year old is wont to do), then toast it, you’d better grab either some marshmallows or a fire extinguisher.
Whatever you do, don’t try to throw flour on it to put it out, like my brother did - this will only make a fireball that will singe your eyebrows off.
You have to butter it before you eat it.
My brother also saved the OP the effort of doing this experiment by setting fire to the toaster back in his childhood.
I should point out that it was not my brother who posts here, but the other one, whom we may mock with impunity.
I was, I think, about six when I asked my mother this question. She said not to do it. I went with that.
Roddy
DO NOT DO IT!!! You’re likely to start an arms race with the folks on the other side of the wall.
[moderating]
Since this is about food, I’m moving it over to Cafe Society…
[/moderating]
Only if you want two buttery bread missiles shooting out off the counter and on to the floor. And of course as we all know, toast always lands butter side down.