Most of them can be made with the cunning use of colons. If you hover over the button, a word or series of words appear. If you place these (or a variation of these) in between two colons, the smiley will magically appear.
Here's a list I've managed to compile. I'll type out what was placed in the colons after the smiley appears.
:veryhappy: (does work with a colon D
)
smile
sad:surprised:
:surprise:
:shocked:
(shock):confused:
cool:laughing:
:laugh:
mad
razz:embarassed: (sic)
:embarrassed:
:crying:
cry:verysad:
evil:verymad:
twisted:rollingeyes:
wink:exclamation:
:question:
idea
arrow
neutral
mrgreen