What happens when your companion dies on World of Warcraft

For all classes, loss of a pet is not a great problem. Hunters have Revive Pet, which allows them to resurrect their pets. Warlocks and Death Knights, as well as Frost Mages, can simply summon their pets again using the normal abilities.

In the pen-and-paper game, such options are rare or nonexistant (except maybe for warlocks) and you'd have to tame a new pet to regain access to it.