Here in the real world, talk show host and "cousin"* Conan O'Brien won a walk-on role on 'How I Met Your Mother' at an auction. The producers offered to beef up the role for him, but Conan turned it down. I think he thought it would be funnier to just do the microscopic cameo without any fanfare.
So in his blink-and-you'll-miss-him moment in 'HIMYM', here's Conan.....
I'm going to count this as an appearance by Conan O'Brien as a member of the League of Themselves. Apparently, Coco came back to New York City and decided to hang out with some old friends at MacLaren's, which must have been one of his favorite watering holes while he lived in the Big Apple.
In a world where the televersions of celebrities can find themselves in the middle of nowhere for the flimsiest of reasons in other sitcoms, this was at least feasible.
As such, his walk-on now connects 'How I Met Your Mother' to the following shows:
"The Rutles 2: Can't Buy Me Lunch"
And that's just in Earth Prime-Time!
His appearance in an episode of 'DAG' takes place in the same TV dimension in which you'd find 'Karen', 'Hail To The Chief', 'Mr. President', 'Cory In The House' and the upcoming 'Veep' on HBO. In Skitlandia, he can be found in an episode of 'The Martin Short Show' and 'Mr. Show with Bob & David'. (I think his opening routine when he hosted the Emmy Awards - in which he woke up late and found himself in various TV shows - should also be included here.)
Over in the Tooniverse, Conan's cartoon counterpart could be seen in 'The Simpsons', 'Dr. Katz, Professional Therapist', and his live-action doppleganger was beamed into the Tooniverse in an episode of 'Space Ghost, Coast To Coast'. (So that should count as half a credit for him in his tally for the main Toobworld.
And nearly one thousand years in the future, his head will be cloned so that he can work the Catskills circuit in a Christmas episode of 'Futurama'.
Just another example of life during prime time......
* All O'Briens are related. It's the law.