A blackout, or bump, is a crucial type of sketch incorporated into any good sketch review. It is basically a two-liner joke portrayed in sketch form. It only lasts a minute or two at most, and serves the purpose of breaking up action between sketches. Although shows such as "Saturday Night Live" don't rely on blackouts, many theatrical sketch shows do. Learn how to write a blackout sketch.
Think of a strong set up. This is much like writing a standard two-line stand-up or monologue joke. If you are lacking in ideas, consider reading the newspaper and trying to pull something out of the headlines.
Ponder the irony in the set up. What is it that is funny? Can you heighten the set up to the absurd? Can you play with a character in the set up and put him or her in a fish-out-of-water scenario?
Write the punch. This should take the ironic idea you thought of and put it into action, whether it is words or physical action.
Read the whole piece out loud. It should be short, no more than a minute. Does it flow well? Does the punch seem like a natural ending to the sketch?
Find actors to do a reading of your sketch. Watch it and take notes. Is it funny? Is it too long? What works and what doesn't?
Edit your sketch based on your notes.
Create a final copy of your sketch. You just wrote a blackout sketch.
Blackouts don't have to be elaborate. In fact, the simpler the better. If your blackout is only several lines long, then you're probably doing it right.
Make sure your blackout isn't too long. It should only run about 30 seconds to a minute.