The worst joke I ever heard was about the Foo Bird. I’ll not repeat it here. Yours is bad enough, thank you.
That one would be off-limits here due to the punchline. :^)
I heard the Foo Bird before the Shelly joke.
And just before the Foo Bird, I heard the one about the rabbi walking down the mountain...
The first switcheroo pun joke I heard was the one about the golden dragon, the princess, and the castle. :^)