Can anybody explain the punchline of this joke?

I just received this joke in an email and I don't "get it"... neither does the person who sent it to me. Maybe I'm a bit slow today, but I don't get it. Can anyone explain?

Shrek, Brad Pitt and Angelina Jolie were all having lunch together.

Shrek said, 'I have always thought that I'm the strongest man in the World, but how can I be sure?

Brad Pitt said, 'I'm pretty sure I'm the hottest man alive but I've Never had it confirmed.'

Angelina agreed. 'I'm told I'm the sexiest of them all, but Sometimes I wonder.'

They all decided that the best way to find out if their beliefs were true was to approach the wicked Queen's mirror to confirm for them whether Shrek was the strongest, Brad Pitt was the hottest and Angelina Jolie was the sexiest.

They agreed to meet again the next day for lunch to discuss their findings.

The next day Shrek walked up with a smile. 'Well, it 's true. T he mirror told me that I am the strongest man in the world.'

Brad followed and boasted, 'It is true, it has been confirmed that I am the hottest man alive!!'
Angelina walked in, head bent, tears in her eyes and asked, "Who in the hell is Ms. Rocki!?!"