He stole a joke from Jimmy Fallon
After the recent Sesame Street firings, Conan joked that these firings "were brought to you by the letters F and U."
That same joke was told by Jimmy Fallon on an SNL Weekend Update sketch years ago, when Sesame Street had a round of layoffs.
This kind of creative overlap might be forgiven, except for one thing: The Fallon joke was specifically referenced in Bill Carter's book "The War For Late Night," which Conan was interviewed for (and everyone working in late night has read). There's no way Conan and his writers could be unaware that the joke was Fallon's. They told it anyway.