I'd like to say that they mysteriously appeared in the kitchen but me Mam bought them for us from Tescos. They look like brown paper bags but I expect they're made out of asbestos or something.
You put a sandwich into them, pop it in the toaster and it makes a toasted sandwich without fannying about with the grill. Apparently, you can also cook oven chips, fishfingers and salmon fillets in a toaster using these magic bags.
No washing up or anything! Why weren't these invented when I was a student