There's an old Yakov Smirnoff joke that goes something like, "in Soviet Russia, it's freedom of speech. In America, it's freedom after speech." And if there was anyone who knew this first-hand, it was Smirnoff himself.
He and all other comedians who used to live under the Soviet regime could have faced jail time or death for any joke deemed "unfit." In order for this to work, there would be absolutely no improvisation. All comedians would need to run each and every joke they planned on telling in a given year through the Ministry of Culture of the USSR.
Within the Ministry, there was an elaborate department dedicated to jokes and humor. The process of telling a timely joke without angering the committee was exhausting. Any joke that was
actually funny against the communist ideology was banned. Even being remotely anti-communist meant the joke was banned.
Smirnoff told The Guardian one of his jokes that didn't make it through and you can see how "humorous" of a place the Department of Jokes was.
"An ant falls in love and marries an elephant. They have an amazing honeymoon, a night of wild passion that is so passionate, in fact, that the elephant collapses and dies in the middle – the ant, however, is even less lucky. He is forced to spend the rest of his living days digging the elephant's enormous grave."
Apparently, that's anti-communist and needed to be banned.
Because jokes were so generally unfunny, scarce, and hard to get approved, any joke that was both permitted and remotely humorous was immediately borrowed by every other Soviet comedian. Talk show hosts were heavily vetted before being allowed on air, so their works were free game and any joke they told would end up in every comedy club a week later.
This doesn't mean that rebellious citizens didn't tell their own jokes. Ukrainians held a deep resentment towards their Russian overlords so their jokes were more common — if not darker.
"A Soviet newspaper reports: Last night the Chernobyl Nuclear Power station fulfilled the Five Year Plan of heat energy generation... in 4 microseconds."