Alibi
"Fred and George Weasley!" Mrs. Weasley shouts from across the house, clearly furious. The twins' eyes widen and they make a break for it. Just as they're about to apparate, Molly throws up a decent ward against such things in her effort to keep the two present for their scolding and punishment. She knows not to involve their father, for he would only scold them after a compliment or two, which is not what she wants.
"Mom, you could have splinched us!" Fred calls dramatically, hoping a bit of a guilt-trip will lessen their punishment. At that moment, Molly storms into the room, looking to be in full ranting mode, dripping wet with a very sticky and multi-colored goo.
"I'd have been satisfied if I had!" Molly shouts. The twins wince, wondering if they went too far. Getting her is fine, they'd done it loads of times. But, getting her and her precious kitchen at once might have been the straw that broke the thestral's back. The twins scratch the back of their heads in unison, looking at the ground shamefully.
"We're sorry, mum," Fred exclaims.
"Yeah, really," George continues.
"It's all in good fun," Fred tries to convince, only to realize too late he said the exact wrong thing. George nudges him harshly in the side with his elbow and winces as Molly's face reddens in even further anger.
"All in good fun?" Molly asks. "All in good fun? My kitchen is now covered in this-" she breaks off, gesturing to the goo covering her. "And you say it's all in good fun? I'll have you know that keeping the kitchen clean with a house this full is difficult normally, and then you go and pull something like this. Is there anything you'd like to say for yourselves?"
"The truth is-" Fred begins.
"It was actually Bill and Charlie," George continues. Molly gives them an incredulous look.
"They're upstairs now, and you know that's where we got out pranking streaks from."
"They did it this time, mum, but since we always prank these days-"
"-we thought we could cover for them."
"But then you got really mad, and…" George trails off, seeing Molly's expression still filled with doubt.
"We have alibis!" Fred suddenly exclaims. Molly raises an eyebrow and the twins grin in unison.
"I was with Fred, in the sitting room, playing Exploding Snaps!" George claims.
"And I was with George in the sitting room, playing Exploding Snaps!" Fred agrees. Molly's face now shows slight amusement, probably at their – for once – horrendous lie. She quickly calls her anger back, though, ready to deal out punishments. The twins groan in unison after seeing her expression change. They really should have bribed Ron into being their alibis today. Maybe tomorrow…