That’s my seat

But they chose that seat. Assigned seating sucks because someone else chose where you sit.

Sitting in a different seat every lecture can get hilarious when there are only 10 people in the lecture or if there are 200 in the lecture. The 200 takes longer, but gets funnier the longer it goes on, as you just randomly pop up 3/4th's of the way through the semester next to someone who has never seen you and you can see them visibly ask themselves "dafuq"? The key is to keep quiet though, otherwise you'll attract attention and it won't work.

Literally no one picks a special spot to sit in at my university

In one of my first Lab Pracs I made good friends with the 3 other people sitting around me (it's like a silent rule that once you choose your seat, that's it, that's your seat). On one of the pracs these 2 random people stole our seats and it messed with the entire table seating and everyone was confused.