River's stuffed platypus when interacted with as a memento
The Stuffed Platypus is an item in To the Moon. The player may pick it up when they visit the "funny room" in the Wyles' cliff house early in the game. It is a plush toy belonging to River Wyles, which she was greatly attached to—in John Wyles' memories, River is hardly ever seen without it. Later, it would turn out that the platypus was a gift from Johnny, who won it on a mini-game at a carnival when they were children.
The "funny room"
After the deaths of River and Johnny, Sarah Quinn, the daughter of Johnny's caretaker Lily Quinn, reveals that she has become the caretaker of the platypus, and that his name is Plat-Plat.