Love this show. I watched the new episodes a few days ago since the original episodes were my childhood. Absoulutely amazing.
There is a lot of realistic gore, so I don't recommend if you are icky about that stuff. There is some swearing, but a very minimum amount, and not extreme vulgar words.
If you like horror, surrealism, and comedy then this show is perfect for you. At the beggining of the episodes, it tries to protray a cutesy, Seasume Street-like puppetry show, but once you get into the episodes, it expresses how much dark themes* they include in the plot. To also add onto the child-like protraying scenes, they always have a song in their episodes in which ends in some dark, disturbing manner.
Themes include: Gore, getting old (dying and illness), cults, mental illness, etc.
I really recommend this show if you are interested in said stuff.