Everlasting Gobstoppers

Then he ran over to another machine, a small shiny affair that kept going phut-phut-phut-phut-phut, and every time it went phut, a large green marble dropped out of it into a basket on the floor. At least it looked like a marble.

'Everlasting Gobstoppers!' cried Mr Wonka proudly. 'They're completely new! I am inventing them for children who are given very little pocket money. You can put an Everlasting Gobstopper in your mouth and you can suck it and suck it and suck it and suck it and it will never get any smaller!'

'It's like gum!' cried Violet Beauregarde.

'It is not like gum,' Mr Wonka said. 'Gum is for chewing, and if you tried chewing one of these Gobstoppers here you'd break your teeth off! And they never get any smaller! They never disappear! NEVER! At least I don't think they do. There's one of them being tested this very moment in the Testing Room next door. An Oompa-Loompa is sucking it. He's been sucking it for very nearly a year now without stopping, and it's still just as good as ever!'

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Charlie and the Chocolate Factory, Chapter 19