Hello Nurse!

Hello Nurse! is a Halo 4 achievement added with the Castle Map Pack. It is awarded when the player, in Castle DLC matchmaking, heals a near-death teammate with a Regeneration Field 5 times. It is represented by the Regeneration Field icon with a number 5.

Trivia
The name "Hello Nurse!" is a reference to a popular vaudeville catcall later re-popularised in the 1990's cartoon show Animaniacs.