There are a couple of harness racing tracks in Maine.  It's pretty common to see those guys on the Interstate with all the horses' heads sticking out the drop-down windows.  Whenever I see that, I want to do unspeakable things to the drivers. 

I once saw someone start to drive off with the horse tied to the outside of the trailer.  Thankfully, they looked in their rear-view mirror before getting over 5mph.

I knew one lady who bought a tiny short/skinny old BP trailer with a single butterfly vent in the nose and slats on the sides/rear.  She painted the whole thing (inside and out) dark brown, put plexiglass over all the slatted openings, used old rolling-up conveyor belt for the mats (no shavings), and then wondered why ol' Dobbin' didn't want to get in it. 

Then there's the standard stuff, like hitching a BP trailer LITERALLY to a ball on the bumper of an old truck, instead of to a receiver hitch... or driving down the road with the front of the trailer so much higher/lower than the back that you were afraid they'd dig the bumper/nose right into the pavement.

We were  at a trail head once.  Most of us had ridden and were lofing around visiting with others.  A trailer pulls in and a camel got out.  My horses have never been bothered by Llamas, cows, mules.  But they didn't like the camel.

The old rancher came by and saw it and said. I'm so glad I saw that thing here in the parking lot.  I would have been puzzling for days, wondering what those tracks were on the trail.

I saw a loose horse lay down and roll near a unhooked ATV/Toyhauler trailer. The horse got cast under the hitch.  As it thrashed and tried to get rolled over, it busted the heck out of the generator and put big horsehoe dents in the trailer side. Eventually the horse cold cocked himself on the tongue and I was able to drag him out from under the tongue before he woke up.

Several years ago I had a lady customer whom purchased a new bumper pull trailer from me.  She was a "newbie" to the horse scene, so I went over evrything with her very thoroughly in regards to her new trailer.  I showed her how to hook it on her receiver hitch, and attach tow chains, safety cable, etc.

Several months later she happened to call me and tell me that she had taken the receiver insert and ball out of her truck for about two weeks; and when she put it back in the receiver she turned it upside down.  So, the nut and bolt part of the ball was facing up.  She hooked her trailer on that, and pulled it for 5 miles, AND IT NEVER JUMPED OFF THE NUT !!  She said that somebody at her boarding barn pointed it out to her, or she probably would have kept pulling it!

The horse in the back of the truck is one I've heard before.  Used to be somewhat common place, I believe, before we all had trailers.  I remember reading an article about a lady who, back in the day, would haul her horse to events in the back of the pickup and unload him, then use the bed of the truck for her bed.  Knowing they would be sharing, she apparently had trained the gelding to do his business on command, thus keeping the truck clean.  Don't remember who it was anymore.

Weirdest thing I've ever seen...there was a trailer at a horse show, parked off in the field for overflow parking.  Brown, steel and rust, 14' bumper hitch.  The top of the trailer had long since rusted away, and it was covered in a canvas tarp held down with twine.  The tarp had lost a battle with a dog, a family of moths, or something, and it looked like a 4 year old had been given the job of tying it down.  The door latch was held closed with a bungie.  The trailer leaned quite markedly to one side. I assumed someone had parked it there and given up on it years before, so you can imagine my surprise when a teenage girl, who'd done quite well all weekend long, showed up on Sunday evening to help her mom hitch the trailer and load her horses in it.  They would have been safer in the back of the truck.

We arrived at a small camp to find a couple of emus living in the run between the camp two turn-out pens.  Needless to say none of the horses were thrilled with the sight, sound or smell of the creatures.  I decided to adddress the issue early in the trip so the next morning before we rode I put my four geldings in the turn-out.  Hay was placed right in front of the fence by the emus.  It took a while for things to calm down, but after about 15 minutes hunger won over the horses and they decided the "big birds" were not going to kill them or eat their hay.   After dealing with the emus the llama she had didn't seem near as scary. 

As far as trailers, we were coming back from a trip and were following another LQ trailer.  One of the wheels came off going down the rode and flew across 5 lanes of busy traffic.  Hit the median wall and rolled for what seemed like forever.  Smoke was boiling off of the tire.  No one hit it.  No horse got hurt.  We pulled over and called for help.  The officer whom arrived happened to be a mounted patrol officer.  He blocked the traffic to retrieve the wheel/tire and brought it back to the owner.  Another trailer took the horses on home and everyone got home safe with almost no damage to the trailer that lost the wheel at 65 mph.  After that weekend we learned how valuable US Rider could be.

Back in the 70's, I remember a guy that showed at all the local shows...had a two horse straight load gooseneck....and a Cadillac Sedan de Ville. I can't remember the exact setup on the ball, but it was over the trunk lid. And the big Cadillac that pulled the 4 horse head to tail bumper pull. Swivel tongue just like the 2 horse inlines were. Miley or McQuerry made it. Actually the amount of cars pulling horse trailers at the shows then was huge. One horse trailers, side by sides, two horse inlines were all common. 5 wide, 6 tall on most of the side by sides...we were hauling 16 hand horses in 6 tall trailers. Lean against the door to get it closed. How times change...

And racks in trucks were still fairly common then too.

You can still haul in your pick up trucks if you have mini s

http://www.miniaturehorsehaulersbybob.com/2_horse.html