A tiny white dot had reappeared at the end of the painted tunnel, and now Ariana was walking back toward them, growing bigger and bigger as she came. But there was somebody else with her now, someone taller than she was, who was limping along, looking excited. His hair was longer than Harry had ever seen it: He appeared to have suffered several gashes to his face and his clothes were ripped and torn. Larger and larger the two figures grew, until only their heads and shoulders filled the portrait. Then the whole thing swung forward on the wall like a little door, and the entrance to a real tunnel was revealed. And out of it, his hair overgrown, his face cut, his robes ripped, clambered the real Neville Longbottom, who gave a roar of delight, leapt down from the mantelpiece, and yelled, “I knew you’d come! I knew it, Harry!“

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