For the uninitiated, MST3K and RiffTrax take horrible movies and add snarky/funny comments to the audio. It’s like a strange drug that transports you to a nerd movie night. MST3K was mostly older B- and Z-movies, whereas RiffTrax takes on recent releases (Twilight, The Dark Knight, the Star Wars prequels, etc.).
Here’s a taste. The first hit is free.