The best comedies all have one thing in common: the characters who populate the story take everything that happens absolutely seriously. Whether they are busting Zuul, attempting to land a pilot-less airplane, or questing for the Holy Grail, they do so with a mindset of absolute sober sincerity. Whether the comedy in question is the erudite pomposity of Noel Coward or the physical absurdity of the Three Stooges, it's all played with a metaphorical straight face; no mugging allowed.
If the characters in our comedies were to react in a manner unbefitting the situations in which they found themselves, the illusion would be broken and the suspension of disbelief would be shattered. For a comedy to truly succeed, it is imperative that the characters react to and interact with their own reality, no matter how ridiculous or insane, in a consistent and logical fashion.
Watching an improv scene unfold with the suggestion of "hair," we saw a customer enter a barbershop and sit down. A bumbling barber enters the scene. After examining his customer's hair for a moment, the barber grabs a chainsaw and starts it up. So far, nothing is necessarily going off track. The customer, however, does not react as someone would when faced with a murderous chainsaw-wielding barber. Instead, he turns his head calmly and comments on how nice the barber's "new chainsaw" is.
Everything then goes downhill precipitously.
Countless appropriate reactions could have presented themselves; perhaps a blood-curdling scream from the terrified customer, followed by a hearty laugh from the barber as he gets rid of the chainsaw and explains it's a joke he plays on all his new customers. Not exactly brilliant theater, but appropriate within the context of the platform they created.
Instead we watch as the barber fumbles about for a moment, suggests that perhaps he shouldn't use the chainsaw, and then lets it disappear from his hands, to evaporate into the ether. The scene meanders on for a bit, but nothing of note is accomplished. There is no miming of actual barber shop behaviors, no discernible characters, and no adherence to the environment created. In fact, there is so little environment created that there is little if anything to adhere to.
The point to be made here is to create your reality, stay true to the reality you've just created, and behave within that environment as characters naturally would. Will all characters behave as normal humans would in all situations? Of course not.
Not all characters
are
"normal" humans.
They must, however, behave in accordance with the character construct you adopt in order for the audience to accept your characters as "real" within the context of the scene. The audience may not consciously sense when an actor is not being true to the reality of the scene, but you can be sure they will sense it subconsciously, and that fact will color their perception of the scene, causing them to
lose focus and drift.
The best comedy is played in all seriousness, from every insane minute of Monty Python to every childlike moment of Pee-Wee Herman's quest to recover his bike. Strive for that mindset, be true to the reality you create, and the humor with come of its own accord.
Happy improvising!
