Data's Character Development: Becoming More Human
I'm watching The Next Generation for the first time (I'm a relatively new fan haha) and I'm over halfway through season 4. It's so much fun to see Data slowly understanding humanity more and beginning to act more human himself. For example, I'm on season 4 episode 18 "Identity Crisis". He first denies that he's worried about Geordi, but eventually says he is "strongly motivated to solve this mystery".
Data is definitely my favorite character, so moments like these are always fun. Plus, I got to see his cat for the first time in episode 11 of season 4.