They move onto green custard right when Ginny comes back from holidaying with a friend. She doesn't tell them it's gross, because of course that'll just make it *worse*. She does say, "green, huh? Trying out for Slytherin?"
The next morning, Fred and George sport identical bowls of red custard. She can't help but feel a small surge of triumph.
"Really, you two," Molly Weasley complains, "there are other foods in the world other than baked potatoes!"
In unison, they start complaining - "but mum, it's this cracking good american cookbook, look!" and then, "and filling, it's not candy at least!" - and Ginny surreptitiously sprinkles the chives and bacon on top of their sour cream.
When they realize, in unison they're furious, of course. They immediately turn on Ron, trying to make him eat the rest of the bowl of chives. Molly starts yelling, Fred and George get sent to bed without any more dinner, and Ginny gets two extra stuffed baked potatoes for dessert.
It's the Jelly Slugs when Molly puts her foot down.
"You will not eat Jelly Slugs for dinner, boys."
They don't, to be fair, eat just Jelly Slugs. Somehow, however, the candy makes their way into the gravy, the roast potatoes, and stuffing as well. Molly pulls a root beer flavoured one out of her carrots before she really starts yelling, the twins protesting they kept them to their own plates.
Ginny swaps her plate for George's while no one's looking, and eats the leftover roast beef and gravy. It only tastes a little like root beer.
"I think," George says, eyeing Ginny at the table, "that you're up to no good."
Ginny shrugs. "Me?"
He's instantly distracted by the dinging of the oven, and with yelling to Fred about the scones being done for tea. Ginny takes pity on them and lets them eat three apiece - twice a day for a week and a half, scones and strawberry jam - before she casually says, "Wasn't Angelica saying last term at practise that scones weighed heavy in your stomach? Have you been practising this week?"
They turn to stare at the plate, and then mournfully push it aside, George uttering a little sniffle as he put the lid back on the jam pot. Ginny doesn't even have to wait until the scones are cold before the two of them are on their brooms, tossing a Quaffle at each other. She picks up the knife, and tucks in.