All writing is basically the same: beginning, middle, end. The difference with sketches, and why sketches are actually harder, is that you generally have to establish an entire new world every few minutes with its own rules, get to the joke premise, explore that premise, and then end the thing all within tight time constraints.
“Charm sometimes has a habit of taking its leave of you.”
—Charles Baxter, Believers
Brave, 2012 (dir. Mark Andrews, Brenda Chapman)