how many decades ago did it air
About four or so.
1. It was a very popular show, but had very stiff competition, so it only lasted for two seasons.
2. One of the main characters was played by two different people.
3. A few movies followed it in succession, with at least one of them with the original cast and crew.
4. One of the last shows to be completely filmed in black-and-white from beginning to end.
5. The show's main character (CHARACTER, NOT the actor) was recently the victim of identity theft in the real world!
6. This show made it feel like Halloween was everyday... that right there probably gives it away.