Oh this thread is such a good laugh.
I went into the wrong lecture in second year, I do International Business and ended up in an Engineering lecture where they were talking about air con and ventilation systems! I was too embarrassed to leave so I stayed and sat on my own, and even pretended to sign an attendance sheet they passed around.... I also took notes.... I was worried that the lecturer would ask me questions because I was sat right in the middle, it was so funny thinking back though because I had the most awkward expression on my face the whole way through and got texts from people asking where I was, having to explain was too difficult.
Another REALLY embarrassing incident in first year was when I arrived late to another lecture and I couldn't get to where my friends were sitting so I sat on my own, I was speaking to them on Facebook chat when one of them told me that they had arrived back to their room in halls last night to find a totally random drunk guy asleep in their bed and after they called the residence desk to throw him out they realised he had also pissed in their bed, I started was pissing myself laughing and the harder I tried to stop myself the more I would spaz out, I then heard them across from me laughing at me laughing, and it all just went to **** from there, I was so red with embarrassment and spent the rest of the lecture with my head down mostly in my hands...
One of my more recent ones was at the toilets in Edinburgh Station, it was so busy as well, I put my 30p in the little money slot and tried to get through the barrier but I couldn't and after 2 or 3 tries I noticed it had spat my 30p out, so I put it back in and it was accepted, but I still couldn't get through the barrier, there was a queue behind me and I got really flustered and said to the person behind me 'Oh man this thing's not working!' before I realised I had put my change in the wrong money slot for that barrier (there's two), it was so busy that it was difficult to get out of the barrier to go into the next one, and said 'Oh man it was in the wrong one!' - I was so embarrassed and wish I'd just not said anything...