Marx Brothers

Slapstick or physical comedy is more of a visual medium, so it’s very difficult to have it in a book.  So, some of these tips will need some ingenuity if you plan on going with this type of humor.  That doesn’t mean it’s impossible.  Just have to depend on creative description of acts and reactions as well as the reader’s imagination.  If they have an even slightly immature sense of humor, you have a shot.

1. One of the most important factors in slapstick is that there is pain, but rarely injury or blood.  Even an arrow hitting some will just be stuck in them with no spurting.  The person will usually stop for a bit, look down, and then have a delayed freak out over the pain.  Once you include blood and true injury, the comedy is erased because the person isn’t going to walk it off that easily.  I will say the only time you can get away with this is if you’ve established that the character can regenerate or is immortal.  Hence why I was able to do more violent slapstick with my vampires in War of Nytefall.
2. Exaggeration can help in making it clear that this is being done for comedy and not to cause real damage.  Just look at any Three Stooges skit and you’ll see how cartoonish the slapstick is.  Hit in the head with a hammer?  That should kill Curly, but it just hurts with no visual damage.  The reaction to the slapstick should be over the top as well.  A great example would be Chris Farley who would throw himself into physical comedy . . . literally.  His voice would become loud, sharp, and impossible to ignore, which enhanced the effect.
3. Physical comedy doesn’t always need two people.  A person simply has to go through a painful experience, which is exaggerated.  They could fall off a house, get in a fight with an automatic door, or be stuck under a bus.  Again, the whole concept revolves around ridiculousness even if a situation is totally believable.
4. Surprise can be an important factor here.  Shock of seeing someone hit in the groin without warning or falling off a cliff even you didn’t see means your guard was down at the time.  People are more likely to laugh when they aren’t guarded.  Of course, there needs to be some hint that this is possible.  Can’t have a cliff in the middle of a big city, but you could have an open manhole.  Surprsie to the character also makes the exaggerated reaction more believable.
5. Slapstick from one character to another loses some of the humor when hatred is involved.  Sudden anger is one thing because it means the character has lost their temper like Moe Howard.  If there is true hatred behind the violence then the tone is much different.  It means true damage is intended.
6. THE TONE OF YOUR STORY NEEDS TO MATCH PHYSICAL COMEDY FOR IT TO WORK!  Seriously, it doesn’t really match with anything serious.  Those kinds of tones put the readers in a different mindset, so they’ll be thrown off and maybe even horrified by the incident.  It won’t appear comical.  Just painful.
7. Groin shots . . . For some reason, they still get laughs.