They Might Be Giants - Letter Not A Letter

Lyrics:

What's that? 
That is a letter. 
What is that? 
That's not a letter. 
That's a letter. 
That's not a letter. 
That is a letter. 
Is that a letter? 
I don't know what that is. 
That's so a letter. 
What is that? 
Whatever it is, that's not a letter. 
That's a letter. 
Is that a letter, or what? 
That's a letter. Only it's upside down.