There is a bonus objective to save various pets during gameplay, but it is possible that they can be "killed" in the process. Because of the narrative of the game they are brought back to life in each level, so this is not permanent. There is mild cartoon blood involved.
While not mandatory, it is possible to attack fellow player characters in multiplayer mode. It is possible to play as two spouses if you unlock these characters.
While not mandatory, it is possible to attack fellow player characters in multiplayer mode. It is possible to play as a parent and child if you unlock them, but the child is a teen or young adult during the events of the game.
It is possible to teleport inside of a block using a teleporter. You take damage, but teleport out immediately unless you are at low enough health or out of teleporter uses.
One at a certain point of a hidden alternate route the player needs to commit suicide to either uncover a door, or travel to a realm of the dead. The gravity of the action is greatly lessened by using an item which brings the player character back to life immediately though, as well as that in the game's canon, not even death can get one out of the cursed caverns the game takes place in, as they'll just wake up at the start of the cave as if their death was a bad dream.