The song that depicts Ben
 

http://www.youtube.com/watch?hl=en&v=mQZmCJUSC6g&gl=US

I changed the lyrics a bit. The vain bit is that he's always looking in a mirror checking his 'looks'.

You walked into the BB house
Like you were walking onto a yacht
Your hat strategically dipped below one eye
Your scarf it was apricot
You had one eye in the mirror
As you watched yourself gavotte
And Mario dreamed that they'd be your partner
Hey'd be your partner, and

You're so vain
You probably think this show is about you
You're so vain
I'll bet you think this show is about you
Don't you? Don't you?

You had Mario several years ago
When he was still quite naive
Well, you said that you made such a pretty pair
And that you would never leave
But you gave away the things you loved
And one of them was Mario
I had some dreams they were clouds in my coffee
Clouds in my coffee, and

You're so vain
You probably think this show is about you
You're so vain
I'll bet you think this show is about you
Don't you? Don't you?

I had some dreams they were clouds in my coffee
Clouds in my coffee, and

You're so vain
You probably think this show is about you
You're so vain
I'll bet you think this show is about you
Don't you? Don't you?

Well, I hear you went up to Saratoga
And your horse naturally won
Then you flew your Lear jet up to Nova Scotia
To see the total eclipse of the sun
Well, you're where you should be all the time
And when you're not, you're with
Some underworld spy or the wife of a close friend
Wife of a close friend, and
(didn't Ben say he flirted with others wifes hehe)

You're so vain
You probably think this show is about you
You're so vain
I'll bet you think this show is about you
Don't you? Don't you? Don't you?

You're so vain
You probably think this show is about you
You're so vain
You probably think this show is about you
You're so vain
You probably think this show is about you

You're so vain (so vain)
I'll bet you think this show is about you
Don't you? Don't you? Don't you?

Must be....STAR!....Kiki dee I think?

That sounds perfect. Although i think is is more like...

Your so vain. You probably think the world is just for you.