And I'm not sure people are reasonably expected to use a laptop while sleeping. Or an iron. Or a meat grinder. Or a car. Or a water slide.If you call them to report it, don't answer their questions if you do intend to sue (they'll go through a standard list of questions, such as: did the plastic melt, did you smell smoke, did you hear a spark, did you go to a doctor, etc.). It's called CYA: cover your apple as they told us in training.
I'd go to a doctor, get documentation from the doctor. If you want to go the cheap route for a small payout (doctor's bills) and are good at letter writing, demand a settlement from Apple. Otherwise I'd see a lawyer. But see a doctor before any of that. You can get a cheap infrared thermometer gun online and videotape yourself taking the temperature of the computer in the position you were in (they do go above what Apple claims). If Apple mentions their BS about not using them as laptops, show them the stock footage on their website where they show people using them as such. And regardless of whether they try to indemnify themselves by saying it's not a laptop, that type of thing tends not to hold up in court. The court would look at how a person is reasonably expected to use a product.
Sorry about your ball, btw.