Context: The party has just triggered a fireball trap. Players are unconscious, start on death saving throws. Fighter has just failed all three, though DM allows an emergency medicine check, along with a DM roll to determine his fate.
Sorcerer: I got a 14.
DM: You fail to save fighter.
DM: *Rolls Natural 20 on secret roll*
DM: From the corner cave, a giant crab comes and preforms life saving surgery. It performs master CPR. Regain 1 hitpoint.
Table: *Goes crazy*