McGonagall was even keel enough that she blinked at him only once, and the surprise didn't show on her face. It had been so easy - far easier than convincing Miss Tonks.
She cleared her throat again and then nodded once, severely, before picking up her quill again. "I'll let the Ministry know that the position has been filled, then. I'm glad you were so easily convinced, Mister Weasley."