"My rat."

"Ron's rat!"

"Our House Elf's rat."

(Ron pulls his long-suffering straight man face again.)

She titters.  "Is Ron not nice enough to him?"

"They reckon he's smarter than he looks," Ron says.  "All he does is sleep most days."

"We've wanted to pull some experiments on him forever," says Fred.

"Put him in mazes with little triangles of bright yellow cheese and such," says George.

"Little Ron won't go for it, for some reason," says Fred.

"Rats don't even like cheese," Ron says.  "That's a Muggle myth, like rabbits and carrots.  Scabbers' favorite is peanut butter."

"We tried him on some circus peanut butter from Honeydukes once but Scabbers didn't go for that either."

"I don't blame him, that sounds gross!"

"Revolting!" Fred agrees.

Millicent giggles.  She looks very proud to have Contributed To The Banter!

"Fred tried to get rid of the rest of it by sticking it in my Christmas stocking."

"You're Fred, you idiot."

Conspiratorially, to Millicent: "I don't know how he tells us apart."

Millicent has by this point been reduced to a giggling mess.

"They grumble about it when other people do that joke," Ron says.

"Anyway, Scabbers liked cheese when Bill found him."

(Considering how in-hysterics Millicent is Clover decides to do the mouth-twitch she worked out how to do last year that makes it look like she's trying not to laugh.)  "Maybe he got self-conscious about contributing to stereotypes."

"Told you he was smarter than he looked, Ron!"

A tiny little gray-brown head pokes itself out from under Ron's hat!

"Awww is that him?"

Ron's eyes cross a bit as he looks up, and he holds up a hand for Scabbers to climb down into.