There's an old saying about those who forget history. I don't remember it, but it's good.

Colbert’s joke riffs on the famous admonition “Those who cannot remember the past are condemned to repeat it” (often paraphrased as “Those who forget history…”). By claiming he can’t remember the saying itself, he performs the very forgetfulness the proverb warns against, creating an ironic self-contradiction. The punchline (“but it’s good”) satirizes how people invoke historical wisdom as a vague badge of seriousness without actually knowing the content. It also fits Colbert’s broader comedic persona: puncturing earnest moralizing with feigned ignorance, and exposing how slogans can replace understanding.