my sister went on her animal crossing game and found a giant flower by her river. this happened twice. any help on how/why it got there, please post here.
It's called a rafflesia, and it's bad. It means YOU NEED TO PICK YOUR WEEDS. And that's all you can do to get rid of it: Pick all the weeds in your town. Good luck with that.
Fallen Raine is right, but if you want to catch flies, you can let the rafflesia hang around for a bit. Flies are attracted to it, and other than rotten turnips, that's the only way you can catch a fly.