A/N This was a headcanon for Victoria Echevarria :) Hope you enjoy :D
Fred opened his eyes and was almost blinded by the brightness of everything.
I know this place, he thought. And he did know this place. It was King's Cross station. The station he had taken the Hogwarts Express from here for years. But it wasn't King's Cross as he knew it before. Everything was a brilliant white and in the distance, everything was blurred at the edges. This wasn't at all what Fred had imagined being dead would be like. Not at all. He sat up slowly and took a proper look around. Far off to the right he could see three blotches of colour moving towards him. Fred stood up and walked towards the blotches cautiously. He soon realised that the blotches were people. Men, to be precise.
"Hello?" Fred called. His voice echoed around the cavernous space.
"Hello, Fred," a familiar voice called back. Fred sped up and could finally make out who the men were. The first person, the man who had spoken, was Remus Lupin, his ex-professor, fellow Order Member and family friend. The second man was another familiar face: Sirius Black. A much cleaner, tidier Sirius Black than he had known before. It was the third man that surprised Fred the most. Harry?
No, that can't be Harry, he thought. He suddenly twigged who it was: Harry's father, James.
"What's going on?" Fred asked. The three men stopped in front of him and smiled. It was Remus who spoke again.
"We're here to take you on from here," he said calmly.
"Where am I?" Fred said. "I mean, I know this is King's Cross, but, why am I here?" This time it was Sirius who spoke.
"Some people would call this the afterlife; others would say it didn't exist." Fred was more confused than ever and was just about to say so when James Potter spoke.
"We know you are confused, Fred. We just had a similar conversation with Moony over here." James tipped his head to Remus, who nodded.
"It is a baffling experience, I must say," Remus said, smiling. "But we're here to protect you." Sirius stepped forward and looked Fred straight in the eye.
"We, Messrs Moony, Padfoot and Prongs, have been known for a little trouble-making in the past,"
Fred's mind was whirring and matching up facts.
"The map!" he blurted out.
"Yes, the map for example," Sirius continued. "But we lost a Marauder a while back and we're searching for a new recruit." Remus and James stepped forward to join Sirius.
"Me?" Fred queried. He had always dreamt about the makers of the Marauder's Map and what they would be like.
"Will you be our fourth Marauder, Fred?" James asked.
"Yes! I mean, of course!" Fred spluttered. "I would love to!" Remus, James and Sirius laughed. Sirius turned to stand next to Fred and put an arm around his shoulder.
"Come with us then." They started walking. "We'll introduce you to everyone." They walked off into the white haze together.
Messrs Moony, Weasley, Padfoot and Prongs.