You could tie a towel to your back and paste a pickle onto your nose, then go as the caped crusader, Pickle-nose Girl!
But new boots wouldn’t have manure on them. You’d have to plan in a detour to a pig farm…
I love when couples go as each other, and exaggerate their spouse’s mannerisms and verbal quirks.
.
I still laugh about Russell Wilson dressing as his Seahawks coach Pete Carroll (whose grey hair and huuuge wad of Bubblicious during games were famous).
Pete Carroll addresses the gum thing on twitter…
…and his gum tweets on its own!
White (or possibly yellow) shirt— mark with sans serif “COSTUME”
Tada, generic costume
Brian
(Add a penny farthing and could say you are from the village)
And if they have varicose veins they could say they are a road map.
Wear a blue tee shirt and pull it up onto the top of your head. Voila, you’re Cornholio.
My favorite costume was a jellyfish made out of an ordinary umbrella, with additional bits of iridescent plastic ribbon safety pinned at the corners. You can go to the bathroom without unzipping anything cumbersome, and eat without having to take off a mask. Probably add fairy lights if you really wanna have fun with it. Only downside is you have to hold the umbrella up, although it’s fun to dance with so try that.
My favorite easy costume was a magic 8-ball. I had a big 8 on my chest (made out of felt, but paper would work, too). I wrote all of the standard 8-ball answers on little pieces of paper and put them in my pocket. People asked me questions, and then I jiggled around a little bit, just like a real magic 8-ball, and pulled out an answer. Fun and easy!
I remembered another one from my college years: I covered my upper body and arms (separately) with a few turns of Saran Wrap, and called myself a leftover.
Go as your evil twin. Get really wasted and obnoxious, tell all, tell all off, explain it all as just being in character.
Works as lazy plot device in TV and movies.
If you are actually a dickhead, go as nice twin. Not as much fun.
Just saw this. Also relevant.
Wire coat hanger, fake blood/ketchup on the hook: Backstreet abortionist. Topical and offensive all in one.
This also doubles as a Twoflower costume (character from Terry Pratchett’s Discworld)
My go-to costume is a hippie. You said you have long hair - that’s the main part!. Put a headband around your head, draw/paint a peace sign and flower on your face, jeans, vest, some funky sunglasses.
Spray your hair with deodorant and go as an armpit.
I prefer the classic look.
Reminds me of a scene from the Bob Newhart Show, at a costume party (paraphrased, I couldn’t find the scene online):
Howard (looking over at Mr. Carlin dressed in his usual suit and tie): So, what are you supposed to be?
Mr. Carlin: A Revolutionary-era spy
Howard: You don’t look like a Revolutionary spy…
Mr. Carlin (deadpan): Exactly
@Dung_Beetle my wife and I have this hippie tandem outfit. If you’re near San Francisco you can borrow it.
You guys look great, the daisies are a nice touch!
We’re nowhere near you, but I agree, a hippie outfit wouldn’t be too hard to throw together.
Thanks! I thought so too. Impartial, of course. 
Near us are Michaels Arts Supply stores. Places like that would have the daisies and big Peace sign necklace I’m wearing.
1) person with a mustache (all you need is a comb)
2) writer (hold a pen and look thoughtful)
If you happen to have a Space Blanket and some cotton batting it’s pretty easy to make baked potato costume. Just wrap the space blanket around your body with your head and legs sticking out. Use anything for stuffing to get the shape right, close it up around the neck and legs, and the cotton emerging in front. Last time I saw someone use this they stuck a yellow kitchen sponge on the cotton to represent a pat of butter. I suppose you can use a lot of foil instead of a Space Blanket but now you’re heading into high effort territory.
I’m also wondering if the cheap Halloween makeup kits for kids still have instructions for using them to portray tired and offensive stereotypes.