Put yourself in their situation:
It's an event you've been planning for weeks, it's expensive, and you want it to be perfect. So you're on edge. It's crowded, congested, and people are stepping each other's toes. There are long waits for the activities. Children are screaming and hollering all around you. You're stressed out, trying to ensure your children are having a great time. The other adults are going through the same thing, and they're getting intense. And you've had a few beers.
Are you going to let someone deprive you of the fun and enjoyment and magic and fond memories that you paid for? Not a chance. Let's go.
WARNING: Strong Language
A Raging Infection
This cameraman somehow predicted the event of a fight here because we see the argument that lead up to the physical altercation. You can actually see the intense argument escalate, and then explode into a savage beatdown. One man, trying to stop the fight, gets ping-ponged between all the flying fists. Bystanders, drunk with the infectious rage, also try to get some bruises in on somebody. Anybody.
The Solo Artist
This bizarre incident involves a partially disrobed woman who isn't shy to let it all hang out. After the initial faceoff, it's clear that this lady is out for blood on all sides, and all sides are against her. Soon enough, even the man protecting her decides to switch sides, pushing her to the ground. This clip is narrated by an enthusiastic, golden-grill sporting man, clearly enjoying his visit to Chuck E. Cheese.
Babes in Arms
With their fists as swords, and their small children as shields, these mothers get medieval. The video seems to start at the end of an initial altercation, but right when you think she's out the door, she comes charging right back for more. What's crazier is that two more women, who were previously exited, come back for a quick, turn-based blitzkrieg before retreating outside again.
Pizza Love Triangle
We've translated the almost illiterate description made by the video's poster, YouTube user rocslaughter, to mean the following: this fight was between two "baby mommas," whose children share the same father. Mother #1 decides to confront Mother #2 at her child's birthday party for some alleged drama, and then things go exactly as you'd expect.
Up Close and Personal
This cameraman started close to the action. Until, he was too close. After getting knocked by the tornado of hair-pulling, he's still able to capture the interlocked, fighting couple rolling over the hood of an arcade game before hitting the ground together.