Did doofenshmirtz ever miss a Phineas and Ferb episode?

It's impossible for Doofenshmirtz to "miss" an episode of Phineas and Ferb because he is a fictional character in the show! He exists only within the world of the show and doesn't have a real-life existence outside of it.

However, he does appear in every episode of the show, even if he doesn't always have a major role. He is always there in the background or has some sort of interaction with Phineas and Ferb.