"I was on an airplane with three seats per side of the aisle, so it is a decently sized plane. However, it was with Southwest (where there are no assigned seats, it's a free for all), and so because of my height, I always go for the one special row they have where they removed the window seat. So, it is a two-seat row, instead of 3, meaning the window seat in the row behind it has a completely open space in front of it, perfect for tall people and those with leg issues.
I was lucky to be one of the first on and got that extra legroom seat. So, I sat down, put my backpack under the seat in front of me (which was technically 2 rows in front of me, as that's the next seat in front of mine), stretched out my legs, and put on my music as I waited for everyone else to get seated. A couple of minutes after that, a mom who I'd estimate to be in her 40s, came by with her teenage son, each with a backpack and she also had another large bag she was carrying. The mom stopped at the 2-person row in front of me and seemed excited, so she quickly pushed her son into the row and they sat down.
She put one of her bags in front of her seat, and the other in front of her son's. It appeared she then indicated for him to put his backpack under the seat in front of me, and when he didn't, she grabbed it from him and leaned over to put it there herself, but spotted my bag. She talked to her son for a second, he shrugged, and she looked back at me, saying something that I couldn't hear. I popped out my headphones, asking her to repeat herself.
'Is that your bag?' she snapped at me.
'Yeah?' I replied.
'You need to move it!' she snarled.
'What?' I asked, I was legit confused. 'Why?'
'That's our spot!' she shouted. 'You need to move it so that I can put my son's bag there!'
I looked at my bag, then back to her, trying to figure out how she leapt to that conclusion, given that the spot was clearly in front of my seat and not directly in front of either of theirs. There were a few seconds of silence as I stared at her, my brain unable to process her level of dumb and entitlement, as she impatiently waited for me to comply.
'That's my spot,' I replied.
'No,' she said with that drawn out condescending tone. 'It's in front of our row, it's ours, move your bag right now so that I can put my son's there instead!'
When I didn't, she tried to grab it herself.
Thankfully, her son finally spoke up and stopped her so that I didn't have to. Her son was clearly the one with the brains and pointed out it was my spot, not theirs because it was the next seat in front of mine. She glared at him, then at me, got really huffy, aggressively yanked all of her bags up, and stomped away, yelling at her son to follow. They went a number of rows back, though I'm not sure to what end. There was still plenty of overhead storage above our rows at that point, so she would have the same result sitting there or in another row, because it was a sold-out flight, there wasn't an empty seat.
A guy sitting next to me gave me a Wow, what an idiot, sympathy look, we shared a laugh, and I went back to listening to my music."