24. I Will Not Celebrate Meaningless Milestones (Season 5, Episode 19 - Sweet Seymour Skinner's Baadasssss Song)
This was the 100th episode of The Simpsons, and while a lot of shows tend to make a big deal out of this "milestone" by way of a special celebration or a lame clip show, Matt Groening and co. dealt with it in suitably self-deprecating fashion, by noting how ultimately insignificant such an achievement is in the grand scheme of things. Self-awareness at its finest.