As everyone here so far has said, "Sealab 2021" is just hilarious. What makes this show really brilliant is that the episodes follow no particular rules or format. Anything (or nothing at all) can happen and generally does, whether the crew members are striking each other with sticks; the Captain is feeding his Gremlin-like pet "Gloop" liquor, causing it to multiply; or Sealab is invaded by the "Bizarro" crew. (Now that was just friggin' hilarious, with the word "Bizarro" repeated about 100 times.) Enjoy. Adult cartoons don't get much better than this.
Review of Sealab 2021
