A child has managed to melt a Tupperware container full of Play-Doh to the bottom of an oven. How might I clean such a mess and get the oven back into operation?
Though desirable, replacing the oven is not an option.
Most household plastic will become more brittle the colder it is; Tupperware is likely the same.
You could try putting ice cubes on one of the thinner parts and see if it becomes brittle enough to snap. If it does, you could try freezing the whole pile with dry ice. Other freezing techniques include squirting a can of compressed-air dusting spray held upside down. See for example dusting spray. Or if you need more volume, a CO2 fire extinguisher. Spending $30 on an extinguisher is still cheaper than a new oven.
Wear thick leather gloves when trying any of the freezing techniques.
You can probably get rid of the plastic by cleaning with toluene, which is a solvent, though it will probably eat any paint it comes in contact with. The Doh, you can just bake. Toluene is flammable, should be completely removed before turning on the oven.