Unlike the others, Dumbledore stood in the middle of the alley, in his hubris not laying a trap or anything, really. His robes shone, with a steady, low light. The twins whispered to one another behind the barrel, "You think he saw?"
"Not sure, but he's twinkling."
"Assume he saw. Now what?"
"Dumbledore. Transfiguration Master, amused by childish things. Likes to play like he's a dash dafter than he actually is." Harry suddenly noticed that the twins in the room were grinning wide grins, while their Mom was attempting to glare at them. And Snape? he was leaning slightly forward, his perpetual sneer blending smoothly into a smirk. He knows they got past Albus Dumbledore, Headmaster of Hogwarts, but he's wondering how. As am I for that matter.
"If you can't baffle them with expertise"
"show them what a smile will do!" the twins chorused, with wide grins.
Behind their barrel, a cavalcade of rubber duckies began to form. Alongside them, a belljar, a cauldron with chicken legs, and a broomstick that sprouted four arms. As they continued to wave their wands, the cascade of completely implausible objects dancing in place behind the barrel. One twin stood (barely turning to avoid a simple stunner), as he waved them all on.
Dumbledore was dumbfounded, a wide grin suddenly sprouting on his face, as the entirety of the parade gathered him along (tossing him up with their hands, and carrying the old man past both twins).
"Bon Voyage, Professor Dumbeldore" The two twins waved, with scarves in their hands.
Dumbledore gave a booming laugh in return, "Best Fun I've had in ages! Well done, you two!"
Molly gave an audible sniff, and sent a glare at Dumbledore, who looked back, grinning and completely unrepentant. "A truly remarkable piece of transfiguration, Misters Weasley" Minerva McGonagall was hear to say. "I'd have had difficulty downing that many implausible objects. It's hard to find a weakness when the object itself is pure fancy."
[a/n: you don't beat Dumbledore. You turn him against himself.
This is an homage to Paprika, which you should all go see.]