I’m surprised this thread has made it this far without the “I can wear whatever I want” posters popping in.
They’ll probably be here soon.
I used to work at a call center, so there were a lot of people who thought that because they didn’t work face-to-face with the public, they weren’t responsible for their appearance. One girl was fond of Gathering of the Juggalos T-shirts. Nothing like advertising that you make poor life choices at work.
Ok, you’ve teased us, now tell us! 
MsRobyn I’ve worked at a call center as well, so BT;DT, seen the appalling tshirts, pajama bottoms, slippers, even bare feet.
I was at my cousin’s work’s Christmas party as the guest of my cousin’s friend many years ago. It was held in a hospitality suite of a hotel. My cousin was tall and gorgeous at the time and showed up tall and gorgeous, as expected. Her co-worker that came with her was short, “stout” as they say, and looked hilarious beside my cousin. This woman was dressed in a TIGHT stretchy dress and really did look like a “stuffed sausage”, with her short hair all spiked up and face done up like the 80’s. She was clearly trying too hard and even though it was all I could do to not burst out laughing I kind of felt sorry for her.
I won’t make that claim, but I will say that a few years ago I threw out my suits and donated my ties. Once I hit my 50s, I decided I wasn’t going to wear a suit again. If my daughter has a wedding, she knows what inviting me will mean.
for my parents’ 50th wedding anniversary, we hosted a Sunday afternoon reception at a fancy historical hotel in their small town. The hotel has a destination restaurant and regionally famous head chef. We used an upstairs room and had catered hors d’oeuvres, open bar, wine trays and big dessert table. Fancy-schmancy invitations hinted at its fancy-schmanciness.
A cousin’s wife showed up in white gym shorts with butt cheeks hanging out, a stretchy striped tube top and flip flops. I still don’t know if she even realized how bad she looked in comparison to the others there. He didn’t look much better.
At one point she said to me “My kids are hungry. They don’t like those little sandwichy things. I thought you’d have like, ham and potato salad and stuff.” They left after a couple of hours and let us know they were going to find a burger place so they could get some “real” food.
I had the best laugh later, when I got the photos developed. Their kids had grabbed the disposable cameras off the tables and stuck them down their pants. So there’s that.
I worked in a research facility which employed lots of recent grads, and one of the girls there liked to wear a shirt with the slogan “My boyfriend won’t care… because he won’t know.” I’m pretty sure it was supposed to be “ironic” since otherwise she was a studious type, but the effect was pretty jarring.
I didn’t know these people, but they attended my husband’s college roommate’s outdoor (but still formal) wedding wearing tank-tops, cut off jean shorts and flip-flops. The looked like they had just come from the beach. The cherry on top was that the woman brought a huge Dunkin’ Donuts Fruit Coolatta with her, which she slurped loudly throughout the ceremony.
One time I wore a fancy shirt and pants to a wedding instead of a dress. You would have thought I had slapped the bride. It was friend of a friend, we were in the back of the hall, and they were nice trousers…but I learned that there are some things you just don’t do at a wedding. Or at least a large Polish wedding.
When I was little, I was scarred by a lake trip in which a young woman was wearing a bikini without having done any personal grooming. I hadn’t had any sex talks yet and I could not stop looking at the curly hair sticking out in weird places.
I went to a party a few years back hosted by a couple I knew. There was a woman there wearing a t-shirt that said “don’t hate me 'cause I’m beautiful, hate me because I f**ked your boyfriend.”
This was grotesquely inappropriate because, as I and many of the people at the party knew, she was, unbeknownst to the hostess, sleeping with the host.
Had an older cousin that could have easily been called a giant: about 6’7" and 350#. Wore a leisure suit to a family wedding. Not so bad, as it was in the mid-1970s. Fast forward around 10 years. He’d had health issues (now I wonder if he’d had Marfan’s) and lost over 200#. Another family wedding: same leisure suit.
Because…you were expected to wear a dress? 
One of my cousins married a girl who wore hot pants to the wedding rehearsal dinner.
Very visible public service position, very obese (~5’6", 320#) coworker who shows up repeatedly in yoga pants and a thong which rode up to her natural waist, which was a good 3" above the top of the yoga pants. If she’d only worn a shirt which was about 6" longer, it wouldn’t have been quite so awful.
One day the intern I was supervising at my marketing job showed up wearing a black lace nothing-very-much. (And no, we didn’t market “adult” products.) I was just about to tell her to go home and change when my boss walked in and exclaimed about how stylish she looked! I later found out that the intern was the niece of a VIP in the organization. So I never said anything about her wardrobe, which fortunately was never that extreme again.
On a different occasion, I went to a children’s indoor play area in the neighborhood with my son. One man was there wearing a t-shirt depicting monsters slashing people to death. Yeah, super appropriate.
My sister dresses like a homeless person who roots through dumpsters behind whorehouses. Always. Never seen her dress appropriately for anything. If she was at a Grateful Dead concert, she would be the worst dressed.
I used to work in a cube-farm, and “casual Friday” slowly turned into a running joke. Memos were issued after someone showed up wearing footy-jamas.
Some cultures just are not that forgiving about the notion of appropriate dress for special occasions. I have no problems wearing pants, a nice blouse, and flats for a job interview, but I can see where some people think that same outfit is unacceptable for a wedding or some other formal occasion; that a conservative dress, panty hose, and heels would be more appropriate.
At the public liberry one sees some pretty interesting fashion choices. I fondly remember “boobs tucked into pants lady”. Wonder what ever happened to her?
I don’t know if this counts as “inappropriately dressed” or just that it wouldn’t be appropriate anywhere, but a few years ago there was a guy wearing a shirt that said “I’m Not Mr. Right, But I’ll Fuck You Until He Comes Along”. He wanted information, hypothetically speaking, academically, you know? about growing cocaine.
I referred him upstairs to our master gardener and did not warn her. I’m sure she appreciated it. (Little old lady. Gray hair. Bun.)
Yep, I was out of place. I don’t think anyone in the wedding party actually noticed me (I was just someone’s date), but I got a lot of scandalized looks when I got on the dance floor. So I drank a lot and then I didn’t care anymore.