Since I already asked about sweatpants, and no one yet mentioned a wedding a la Friends in Low Places - time to turn things around. Apart from school dances or when you went to traffic school, what is the least formal setting you have been in your fanciest duds?
I went to a Magic: The Gathering event straight after my aunt’s funeral in my best suit.
For better and for worse, my British father thought it would be a good idea to dress up for my driving exam. “Might make the difference with a marginal effort”. I had no problems but looked dumb in a tie at that age…
Disneyland. Back in 1983, Disneyland required suits and ties for the boys and dresses for the girls on Grad Night. I thought it was pretty damn stupid to wear formal clothes on water rides like the Matterhorn and Pirates of the Caribbean, but those were the rules. I understand they’ve relaxed the dress code in the ensuing 4 decades.
Residency graduation back in 1986, we grads (gals and guys) rented black tuxes with white shirts, white gloves, top hats. Did a musical dance number together to the tune of “New York, New York”.
Probably a Southwest Airlines flight. It was right after college; I was flying home after a job interview. I went straight to the airport right after the interview, still in my suit and tie.
Runner up – a college semi-formal. Yeah, a semi-formal is by definition not the least fancy place, but my date and I (and some of our friends) were all in the symphonic band, and had a concert the same night. For the concert I was required to wear a tuxedo and her a black dress. So we just went straight to the dance after the concert in our formal attire, which was by definition fancier than necessary for a semi-formal.
After our wedding, the missus and I strolled into a Taco Bell next door to a punk-rock dive bar in our full wedding outfits. Until that day, I had not appreciated how busy a newly minted bride is kept at her own wedding reception–apparently so much so that she may very well not have a chance to eat until she and the groom leave and drive down the street looking for any kind of food place that’s still open.
I wore a suit to my Mother-in-Law’s funeral.
I was the only one. I felt pretty stupid. I don’t think that side of the family cares for me too much, and they probably thought I was just going for attention. But, no. You dress for a fucking funeral, don’t you?
I was still in my tuxedo from some high school choir concert or another when I was called upon to go into Walmart. I remember distinctly one girl whistling at me and saying, “Ooo, stud alert.” Even I wasn’t dense enough not to realize she was flirting.
- I was six and wore a suit for the plane ride to and from LAX. Air travel was a lot different back then. Never wore the suit again.
Would it still fit? 
Weird, because I did that in 1968 and they weren’t requiring them back then.
A Boy Scout troop meeting. I didn’t have time to go home and change into my uniform after work so wore my suit to the troop meeting (I was/am an ASM). I took off my tie and jacket for the fire building practice but otherwise was still dressed up. Felt kinda foolish in my wool slacks and tailored shirt, kneeling in the dirt with a Leatherman tool and ferro rod showing a group of kids how to light a cotton ball on fire. I doubt any of the boys noticed or cared though.
I had almost the exact same experience. My father-in-law’s sister passed away and so of course I wore a suit to the funeral. Everyone else, but everyone else, simply wore jeans a t-shirt: they all looked like they were going to go do a weekly shopping run at Wal-Mart. My wife’s family thinks me and my family are pretentious rich folks (laff), so I’m sure they thought I was just showing off.
Although to be fair that suit cost more coin than any of the jalopies they drove to the funeral so maybe they’re on to something there. But yeah, you dress up for a damn funeral so I dont really count that little episode.
Although when MY FIL’s mother died I wore slacks and a cardiagan with an oxford shirt to the funeral. Nice enough to be respectful of the occasion but not so formal that everyone was pointing and staring.
In the 80s I knew the owners of a small deli restaurant. My friends and I hung out there almost every day for a couple years. One night my boyfriend and I had been to some formal event and we stopped by on the way home. I was wearing a vintage 50s burgundy brocade dress. Definitely the most I was ever dressed up at the deli.
It was a thing, back in the late 60s/early 70s, to rent tuxes/formal dresses to wear to the high school prom. Also a thing was to stop at Burger Chef/Burger King/McDonald’s afterwards (they were in the same block, so you could hit them all).
Been in many a Chinese factory wearing a suit and tie presenting as the great white buffalo. Loved it when in the meeting I could say, “y’all don’t mind if I lose the jacket, tie and roll up my sleeves to get comfortable do ya?” And then some BMW German guy with an accent you could cut with a knife says “ja, pleeze”. 
Same with me, except in our case we went to McDonald’s. As you said, we really didn’t have a chance to eat any of the food at the actual wedding.
I did go to a Taco Bell in a tuxedo the night of my Senior Prom with my date. We also played air hockey in an arcade at the local mall. I think lots of kids do that sort of thing though, nothing particularly unusual about it.
The beach. In full Victorian morning dress.
After being invited to an out-of-town wedding, I bought a suit for the first time in my life. The night before I was to leave, I put it on and went to the corner bar, just to get a reaction. The bar was run by a tough character, often alongside his beautiful wife and gorgeous 18-year-old daughter who were known locally as Big Mary and Little Mary. So, I strolled into the bar wearing my new suit and Big Mary said with a grin, “Alovem! What’s with you?” I held my head up, raised an outstretched arm and proclaimed, “I’m here to ask for Little Mary’s hand in marriage!” Everyone in the place howled with laughter, including Big and Little Mary, but their husband/father just glared at me. 
I think mrs. dirtball just got so swept up in the general swirl of activity and the excitement of the occasion and the wonderfulness of seeing relatives from out of town she hadn’t seen in a long time that she simply didn’t think about food and then realized she was starving only after we had driven away. I had had a little bit of something at the reception, but by the time we left, I was in an “Eh, I could eat” state.
She did enjoy walking into that place in a wedding dress on a Saturday night and being among a random collection of punk rockers, aging hippies, and a couple of bikers. As far as I could tell, no one paid much attention, which made it all the better.