Fig
The Altruist
There's many cartoons/anime I watched as a kid and I think the most influential and most nostalgic for me has to be classic Tom and Jerry. I love the slapstick humor, Tom's screams (which is how I even remotely got interested in voice acting or studying the VA industry as a whole), and the animation still holds up even to this day. Plus since it's not necessarily a story driven series, each episode for me can be watched just for fun whereas even in other cartoons/anime, some episodes I just don't want to see for whatever reason.