1) The Mystery Skulls
2) Scooby Doo -- Anon Guest
[AN: This puts the gap count down to ONE. Also, I'm assuming you mean the Mystery Skulls of MSA]
Frisk signed, You're new. Hello.
The formally-dressed Skeleton in front of hir glared down at the child. He was apparently nodding to a beat that Frisk couldn't hear. He didn't speak, and that could be because he didn't have a lower jaw.
Frisk tried offering him some monster food. A candy that ze had saved from the bowl in the Underground.
This isn't Halloween, yet, kid said a voice that was not quite a voice.
Oh. So he was a ghost. I'm sorry, signed Frisk. I got confused. I know someone who can help. At that point, Frisk dialled up Blooky and Mettaton.
What are you doing?
It didn't take long, at least, not for Napstablook. Ghosts could be anywhere they liked in the space of a thought. Mettaton, emotionally attached to his robot body, had to travel through physical space, but... they all knew a boatman. Or boatwoman.
Between Blooky's shyness and Mettaton's showmanship, they got the new ghost talking about his issues, with Frisk playing the role of mediator. Mettaton kept using Frisk like a talking stick, and keeping contact with hir while he raved.
Ambassadoring wasn't always easy.
But Lewis (what an odd name for a ghost, it didn't even end in 'blook') detailed that he was only very recently dead. The remains of a human's determination, fuelled by revenge and more than a modicum of rage.
He was looking for his friends, who were still alive. The love he'd lost, and the one who... might... have killed him. Lewis was foggy on that point.
Frisk told hir ghostly friends to stay with Lewis. Ze had to find Arthur and Vivi and do some mediation. Ze was the Ambassador for all monsters, and this was hir job.
It had been quite a chase, but now the Skeleton of Ebott Mountain had been well and truly caught.
"NYA-HA HA HA!" Cheered the Skeleton. "YOU HUMANS ARE EVEN BETTER AT HIDE AND SEEK THAN FRISK!"
"...ride an' reek?" echoed the dog.
"Uh," Fred shrugged. "Okay, gang, it's time to see who this monster really is..." He reached under the chin for a mask, and at that point, a small child landed on his arm and almost knocked him over.
"FRISK! OLLY OLLY OXEN FREE, RIGHT?"
Frisk, still in Fred's capable arms, signed urgently, This not monster, this friend! No kill!
"THERE'S NO NEED TO BE ALARMED, SMALL HUMAN. I, THE GREAT PAPYRUS, CAN DISCONNECT MY HEAD FOR UP TO SEVEN MINUTES! THAT'S A SKELETON RECORD."
Fred put Frisk down, and ze immediately went to loosen the ropes.
"THANK YOU FOR THE GAME, HUMANS," said Papyrus. "AND DOG. THIS HAS BEEN A GREAT WORKOUT. I SHOULD TELL UNDYNE ABOUT YOU."
Frisk very urgently signed, No, no, no, no, don't you dare! We need them all to live. Peace between monsters and humans, remember?
Papyrus was approaching seven feet tall, which was impressive when he stretched. Then he leaned down to the diminutive Frisk and attempted a murmur. "IS THIS ONE OF THOSE SOCIAL FLAW THINGS?"
Frisk nodded as ze signed, Sorry.
Papyrus had a map for the gang. "THIS WILL SHOW YOU WHERE THE GENUINE MONSTERS HANG OUT," he said. "GOOD LUCK FINDING YOUR FRIEND!
Shaggy watched them leave, hand in hand. "Like... that went differently from what I usually expect."