If your toaster is wide enough, and your imagination is big enough, you could have created the Toastabag. Instead, Dutch firm Boska came up with it.
Basically, the Toastabag is a parchment-paper-like bag that enables you to make an evenly cooked grilled cheese in your toaster, without the imagined mess.
Videos speak better than text, so look on:
Want to buy one? Head over to the Boska website for more info.