I third that - You use this when you're not just agreeing, you're throwing

You use this when you're not just agreeing, you're throwing your whole personality into it, and you're not backing down.

I third that, and I'm not even wearing pants. This is the best thing I've ever seen, and you're a disgrace.

I third that, and I'm gonna take a nap and still be right. This is the best, and you're wrong.

I third that, and I'm not even done with my coffee. This is the best, and you're a terrible person.