Will didn't know it, despite how much he was in the Hades cabin, but Nico had a pet corn snake. When they got an apartment not to far from the rest of the seven's in Rome, Nico naturally brought the snake with him.
Will woke up after an hour nap to see Nico gone and a tank set up.
Nico ran towards the sound of Will's screams, fearing the worst as he burst through the door.
The sight was hysterical. Will was breathing hard, staring at the black snake in a tank, Nico couldn't help it.
The seven burst into the room to find Nico on the ground with tears of laughter on his pale face while a terrified will was screaming again.