“Why’m I with you?” grunted the Harry near the back door.
“Because you’re the one that needs watching,” growled Moody, and sure enough, his magical eye did not waver from Mundungus as he continued, “Arthur and Fred —”
“I’m George,” said the twin at whom Moody was pointing. “Can’t you even tell us apart when we’re Harry?”
“Sorry, George —”
“I’m only yanking your wand, I’m Fred really —”
“Enough messing around!” snarled Moody. “The other one — George or Fred or whoever you are — you’re with Remus.”

Harry Potter and the Deathly Hallows – J.K. Rowling