When should I use supercalifragilisticexpialidocious?

The only use for this nonsense Word is to cite it as an example of certain kind of nonsense Word. It is a school-boy's delight, cobbled together, for comic effect, from meaningless fragments that resemble the Greek and Latin prefixes and suffixes of learned discourse, with a native English ending. For better, funnier examples of this, read James Joyce.