Today in b-days

I got a lot of nice feedback from my last puzzle. Maybe go play that instead of this puzzle, which is what happens when you have an idea so unfunny and ungood that you force yourself to unleash it onto the world, as a way of telling your brain: NO! Never again!

Anyhoo, happy b-day to our special guests, 1-Across, 7-Across, 19-Across, and 20-Down!