Along the same lines – another common trope is the roughneck friends who tear it up in spontaneous fights but then make up and drink some more together. (E.g., Thin Lizzy, “If the boys wanna fight you better let 'em.”) I’ve never seen anything remotely like this happen, but I don’t exactly hand out with that kind of crowd. Does it really happen?
On a similar note, I was a “victim” of an attempted mugging by three street kids, probably aged around 12.
They produced a knife and asked for my wallet.
Unfortunately for them I had earlier ingested a fairly large amount of Amanita Muscaria (Fly Agaric) mushrooms. This is a delerient psychedelic (not really “fun” so not recommended)
And worse, I had stolen some of the decor at the party I had been at.
So these boys, at 04:00 in the morning, then had to deal with a complete madman weilding a papier-mache fish.
I don’t blame them for running away very quickly. In fact I commend them.
In my neighborhood, we called that Irish confetti.
Most of the rumbles that I was involved in were planned events that started on the cruising blvd. They usually took place in a drive in parking lot or a local park. The vast majority of the time the police were tipped off ahead of the meeting time by one of the participant’s that really didn’t want to be involved in a fight but did want to show up to look tough. At these planned events the weapons would come out, mostly chains, clubs, brass knuckles and knives. I never saw one of these actually go down as the police always seem to show up. The worst fights were almost always spontaneous events that took place at local hangouts close to the boundary line of two adjoining cities. In most cases one side would outnumber the other side and the loosig side would quickly retreat following some parking lot skirmishes. But sometimes in cases where tensions had been brewing each side would show up with some of the tougher members. This was almost always fist fights and I did see many serious injuries. Usually guys getting their heads bashed into the ground or some other object.
Early 1980s. I was 19. I, a good friend of mine, and two other guys who my friend knew better than I did went down to see the fireworks over the Detroit River at the International Freedom Festival. We went across the border to the Canadian side because we could legally buy beer at 19.
After the fireworks finished and we were walking back to our vehicle, I saw ahead of us a guy who was having a loud argument with a female, to the point it was turning into a shoving match between the guy and the young woman. My friend stepped in between the two and told the guy to leave her alone. He started attacking my friend, using what looked like ‘karate moves’. No idea if he really knew karate or he got the moves from a Bruce Lee movie, but my friend looked like he was holding his own for a minute.
Until ‘karate guy’ knocked my friend flat on his back on the street (yes, it was an actual street fight, on a section of road that had been blocked off for the festival). He started punching my friend repeatedly in the face with the back of his head bouncing against the concrete, and I thought, “this asshole could kill my friend if I don’t do something”. So I grabbed karate guy and put him in a headlock. I, not at all a fighter, thought “what the hell do I do with him now?” as he squirmed around, trying to break free.
Suddenly, a couple of his buddies came out of the crowd and took karate-movie style fighting stances (I had no idea he was even with any friends- I thought it was just him and the girl he was fighting with). One of them punched me in the face a couple times, two quick pops, and I let karate guy go. They all disappeared into the crowd.
Afterward, the two other guys we were with who I didn’t know all that well talked excitedly about the beat-down they would have delivered if the fight had lasted any longer. One claimed to know karate himself. The other was a 6’ 4" bruiser type. Both had just stood there watching, not doing a damn thing, during the actual fight. 
I’ve broken up fights a few times. The closest to a “rumble” would have been at my local pub. It was a slow night and the bartender had let the rest of the staff go home, since there were only about three regulars there that evening. Then, two different groups of guys, maybe 5-6 in each group showed up. Someone said something stupid, and the two groups started getting a bit fighty, and of course the bartender had to wade into the middle of it to try and calm it down. I decided I wasn’t going to let him wade into the middle of that with no one to watch his back, so I went with him.
I’m a rather large individual with martial arts experience. Lots of people decide to walk away when I show up. Had to grab and hold a couple of the guys, but the rest backed down pretty quickly.