A man recalls a joke about making an elephant disappear, and laughs. He remembers how it was a joke until the day he actually did make an elephant disappear.
"Presto change-o, disappear!" Say that while holding a strange looking stick with a 5 pointed star on the end. Whatever you're pointing the stick at and thinking of will disappear. The same strange stick can also be used to change things into anything else. Transform a mosquito into a dog. Transform the dog into a cat. Transform the cat into a gorilla. Make it disappear. The only problem is that there doesn't seem to be a way to bring anything back after it disappears.
When something disappears, where does it go? It has to go somewhere. What sort of place is that? In a strange sort of way, everything in life inevitably comes back. You can make things disappear for a while, but eventually you'll have to deal with them.
"The wand won't work in reverse."
- the professor