James and Regulus have (gently, lovingly) been ribbing each other ever since Harry was born about what house he'll end up in. Baby Harry spits up on James while he's holding him above his head and Regulus is like "ah, the makings of a true Slytherin." Harry learning to walk and promptly trying to master the stairs, and James is like "ah, brave like a true Gryffindor." Remus and Sirius get in on it, too, of course, and so there's a great amount of anticipation leading up to Harry's sorting.
And then he gets into Hufflepuff.
And Ted Tonks promptly Apparates into their kitchen and goes, "Ha, I win!"
