At the end of The Lorax movie, there's the song "Let It Grow".
The delivery guy starts off the song with this:
You don't know me, but my name's Cy,
I'm just the O'Hare, delivery guy.
But it seems like trees might be worth a try,
So I say, let it grow.
At least, that's how I interpret the name. However, the internet seems to disagree. Googling, there seem to be a lot of dissenting opinions on how to spell his name - is it Cy? Sai? Si? Psy? (See also the totally messed up wiki page.)
Is there any canon info on how his name is actually spelled?