That's the NBC crew in Washington DC. They've been together for years, and crack up like that all of the time. Jim Vance (the one delivering the story) is the coolest! He always laughs at ridiculous things. And believe me, in DC's news there are a LOT of ridiculous things to laugh at!
Now that is just what I needed, a good laugh. Reminds me of the old Carol Burnett shows where the actors themselves could not stop laughing at each other.