In the meantime, the sweets cart has moved on to Lily's, Severus', Alice's, Crabbe's, and Goyle's compartment.
Lily had moved from talking about
Wingardium Leviosa to Houses.
"What House d'you think you'll be sorted into, Alice?" she queries.
"Anything from the cart, lovelies?"
Lily turns to stare a bit at the cart. She knows she really shouldn't, but... she can't resist. She buys two of everything with the money she has, and then a few extra for Severus.
"Dig in, Severus, Alice!"
Little does she know that she's bought James' rigged chocolate frog.
Severus takes the rigged chocolate frog and opens it.
Dungbomb smoke pours out of it and into the car, making Lily cough. She quickly scoops up her things, grabs Alice's hand, and pulls her out of the compartment before it gets too smelly and the smell sticks to all of them.
"Ugh! What a rotten prank to pull! Come on, let's go find out who's behind this."
Severus, in the meanwhile, is miserable. Crabbe and Goyle escape the compartment after Lily and Alice, and they force him to stay in it and get smelly. This was definitely
not how he imagined his first day at Hogwarts starting.