I'm sometimes amazed how both Irony and Sarcasm can completely go over some people's heads. Now, I know that I didn't always understand those two but no matter what I try I'm unable to explain it to a few of my friends.
On another note. I actually think that Irony by Alanis Morissette is ironic. It is a song about Irony filled with things that aren't ironic at all. This has to be some sort of (meta)irony.