I’m in!
Phew! For a minute there, I thought you were someone I used to know. 
Let it all hang out! 
I once made a costume from wardrobe pieces I borrowed from actor friend’s collection. It was the most random stuff ever:
A Dracula cape
A motorcycle helmet (without the face protection, so it was more of a “brain bucket” than anything)
A swim mask
A sheriff’s badge, and
I carried a Barbie doll.
We went to go see Pulp Fiction in the theater, and the guy who was selling the tickets looked at me and asked, “what are you supposed to be?”
I just looked at him and replied, “for what?”
Kim Jong “Ill” - boxer shorts, hospital gown, goofy black wig and giant sunglasses. I can’t remember for sure, but I think I gave myself Asian eyes 
Ugly Betty- Dumpy skirt and sweater vest, frizzy brown wig, glasses, bushy eyebrows and fake braces. I wore it to work where I had only been there a week. I honest to Dog think people didn’t realize it was a costume.
Black Swan- Not that unusual itself but I also dressed my bf as the ugly white swan. Long underwear, tutu, bathing cap. He was a good sport.
I knew a guy who had a stuffed, overlarge stocking and a pot hanging off his belt. When asked, he was “Peter Pan”
The strange one I did was dress in a short sparkly black dress and high heels. I carried a Spud the Budweiser dog stuffed animal. I was Spuds date.
That’s what you call a moving shot in a porn flick. 
Oh, and…
One year at work I had just had chemo and radiation, so I dressed as a skeleton. Alas, I couldn’t find a glowing green costume.
One year I dressed in an academic robe and scarf in the school’s colors, plus a leopard outfit and a wand. I was the only leopard not to be admitted to Hogwarts.
Top hat, bow tie, and tuxedo jockstrap…to a private party.
I used to do pretty good costumes. Lately it’s Zorro most years.
Some of my best-of, from years ago:
- My 9yo brother dressed as a pirate. 13yo me wore an oversized trenchcoat, with a styrofoam head on top of mine, wearing an old-man mask with sunglasses. I just looked like an old guy taking his son out trick-or-treating. When people reached for the bowl of candy, my brother drew his cutlass and chopped off my head. Oh, the shrieks we got.
- I reused the styrofoam head a couple of times. One time, I wore a similar oversized coat, but I put the head on a stick and attached it to a turtleneck. I walked across campus, and “nodded” at people who thought I was a tall man wearing a normal mask. But then, as I passed them, I would slowly rotate the head 180 degrees so it was still watching them as I walked away. Or I would slowly raise the stick so the neck lifted a foot or two off my shoulders. Again: lots of shrieks.
- One more reuse of the head, similar to @blondebear use above: I was a two-headed monster. I did my best to confuse people about which head was real and which was fake.
- Another high-concept costume was the mirror. I sweet-talked some guys at a mirror store into selling me a 1’ square of mirror, with eye-holes cut in it. I dressed all in black and wore that as a mask, and when people asked what I was dressed as, I stared at them and told them I’d dressed as whatever they were dressed as. Or just said, “I dressed up as you,” in a spooky flat voice.
- My last high-concept costume involved a fencing mask and all-white clothes. I carried a sign that said, “Equal work for equal epee!” and “The revolution will not be foiled!” I’ll leave it to the reader to figure out what I was.
- Edit: I just remembered a more recent high concept costume! I bought a plain shirt and a bunch of sequins, and I glued the sequins to the shirt in a square “spiral”: one in the center, then another, then two, then three, then five, eight, thirteen…
I also made a costume for my daughter when she was four that I’m pretty proud of. She really, really, really wanted to be a stickbug for Halloween. With the aid of craft foam, a brown outfit, felt, wire hangers, and two enormous Googly eyes, she was the most adorable stickbug in all history.
At a friend’s Halloween party which had a Titanic theme, my late DH (Kopek) wore my long skirt, chemise, jacket and bonnet, with a fan he held up to cover his beard. His story was “I’m getting on that lifeboat, damn it!”.
At that same party, a man was wearing jeans, chaps, a construction helmet, a leather vest and a few other things I don’t remember. He was The Village People.
Although I was aware of the Python’s three-headed giant, I took my inspiration more from the terrible early 70’s movies The Thing With Two Heads, The Incredible Two-Headed Transplant and The Man With Two Heads (all available to stream for free…if you dare!)
Another one I’d like to try is a rumpled suit, scruffy shoes, a long overcoat, dark glasses, a fedora pulled down over my eyes, and a large bucket of buttered popcorn. The last item makes all the difference.
It’s amazing what you can do with items found in the average closet! 
Cite:
Awwwwwww, duz-duz-duz! 
A woman I once worked with had a daughter about the same age. She dressed her up as a pink crayon for Halloween.
Uh oh, I think that describes what I’m doing this year!
You’ll have an adventure!
Back in 1965, my costume consisted of some eyeliner, an army surplus jacket and helmet, a fake nose/mustache combo and some vampire fangs:
I used to work at a place that had costume contests, and one year I went as my boss: she had just gotten her doctorate, and I wore a white doctor’s coat with her name on it (and a wig: I’m a brunette, and she had long blonde hair). I didn’t win the contest, but she got a huge kick out of it. 
My favorite costume, though, was the year my officemate and I — both women — were the Blues Brothers:
[quote=“terentii, post:53, topic:1009275, full:true”]
I had just moved into my first house the weekend before Halloween and was pretty busy and didn’t have time for a proper costume for a party I was going to attend. While doing some chores I found a long roll of pale yellow floor padding left by the prior owner in my new shed.
I took about fifteen feet, cut some holes here and there, folded over once and stapled the sides, slipped it over my head with my face in one of the holes, and went as a huge piece of Swiss cheese.