This was actually part of a street plot in Season 22, which reran in Season 24. Elmo had lost his imagination hat, and so they went there to look for it. It said "Bureau of Lost _ats," and when they went in, it was like the bureau of lost Bats. Then I think he changed his job, and then it was the bureau of lost Cats. I think then he finally got the bureau of lost Hats. And Elmo described his hat, and everything about it. But the guy was getting sick of it, and said he couldn't possibly find that one hat. Then he quit his job. And then his boss gave him another load of hats (and the imagination hat was in it)! Then he fainted.