Because witches and wizards say the darn'dest things!
Blitz "The Mirror of Erised" if you hear something stupid.
'11 Gryffindor Girl: Did you hear? Some Slytherin chick cheated on her final on the Parseltongue LSA. Snape was the prof that was abroad with them and I think he's going to send her to Azkaban for three terms.
'11 Gryffindor Girl: It was so weird, I saw this guy behind the library chugging a beer under the staircase.'11 Hufflepuff girl: Oh yeah Order of the Phoenix taps.
'11 Ravenclaw Guy 1: So, what are you doing next year?'11 Ravenclaw Guy 2: Well since I had that sweet internship at Gringotts last summer, I'm probably gonna work there writin' checks, makin' galleons.'11 Ravenclaw Guy 1: That's cool. I'll probably just be at the Ministry. Unless I ace the N.E.W.T.s and get into law school.
'13 Hufflepuff Girl: Why was Myrtle moaning so loudly today?'13 Ravenclaw Girl: I heard she got dinged by the Sorting Hat.
'13 Slytherin Guy to group of first-years: Come July, I'll be crushing second-year summer while the rest of you tools are stuck living at the Dursleys'!
'14 Hufflepuff Girl: Well, I was going to take three pre-Auror classes this term, but all those pre-Auror kids are so obnoxious. So I'm going to take Divination with Trelawny instead. Layup!
'14 Gryffindor Guy: Are you going to the party at the Quidditch house tonight?'14 Ravenclaw Guy: I don't know those Quidditch bros don't give out beer fast enough, especially after they lose to Durmstrang.'14 Gryffindor Guy: But all the first-year girls go to their parties anyway
'12 Slytherin Guy to '14 Hufflepuff Girl: Hey, want to come upstairs and check out the Chamber of Secrets?