Something I came up with recently is one of the monsters from Mordenkainen's Tome Of Foes, the Boneclaw, usually attaches itself to a humanoid (a lowly thief, an angry child, a malevolent wizard) but what if it broke those rules and attached itself to the only thing in range, which was a rabbit? Not a lagomorph of caerbannog that can leap 15 feet and rip your throat out, just a particularly angry and evil bunny? Could RP it that it looks like the giant skeletal monster is carrying the rabbit to its lair to eat it, but actually the bunny is commanding it.