I had an android character who was built with no emotions or understanding of human etiquette, but a fantastic ability to learn. Within the first few moments of his awakening he saw one character lift another up (they were siblings) he misinterpreted this as how to say hello and started picking up random people. Unfortunately he did not understand when was appropriate to put them down and spent alot of time just carrying people around against their will. By the end of the roleplay he'd ended up learning mostly female mannerisms and he was a total blast to play :P

One of my favourite roleplays of all time was a dungeon crawl. It was just before the end floor, our characters were surrounded by monsters, there had just been a fight between our mage and a demonlord in our party. We'd fallen through the floor into a trapped room we couldn't get out of, our demon lord was dying, and my character - a celestial - got to basically reach into his soul and bring him back to life as our mage and mercenary fought around us.