Freaks and Geeks (1999-2000)

Freaks and Geeks launched careers of Seth Rogen, James Franco, and Jason Segel, yet NBC aired only 12 of 18 episodes before cancelling this high school masterpiece. With a 100% Rotten Tomatoes rating, it has since generated $2.3 billion in combined box office from its alumni—50% higher than the average drama revival. Its cancellation remains a benchmark for network shortsightedness, as even NBC’s president later admitted it was a mistake 20 years too late to fix.