In an earlier thread, MEH asks:

Maybe I missed the Memo, but what does the IRA have to do with 9/11?

John Thacker gives the correct answer:

There was a (false, sadly) hope that the experience of actual terrorism in NYC might make some of the Hibernian fools realize that it's not so romantic when it hits home, however nice it sounds to struggle against perfidious Albion across the Atlantic.

But Paul Zmrisek gives an answer that is better than correct:

The Irish joined forces with the Jews to carry out 9/11. Haven't you heard of the dread Roth IRA?

Puns are the lowest form of humor. But that didn't stop me from laughing.