[jprete]

Is the word only for unpleasant surprises, or for all such situations, even when the surprising outcome is also a good one?

[dinkblam]

i've never seen it used for pleasant surprises. its basically if you want to show something (even something that does not work, like the engine-not-starting) and the demonstration does not work as expected.

[namibj]

They only have to be "unpleasant" in some aspect, for example because you now annoyed/bothered you team lead. The unexpected behavior itself can still be desired, with the unpleasantness restricted to the demonstration itself.