Justified in the case of Grunt from Mass Effect. Since he didn't technically HAVE a childhood (unless you count accelerated growth in a vat while a Mad Scientist plays context-free videos for you to be a "childhood"), he comes out of the tank nearly fully grown but without a great deal of comprehension of the world beyond "if you squeeze this thing here, the gun goes bang and kills something". As a result, while he's fairly smart, he still plays with action figures, pulls out Buffy Speak on a regular basis, and mostly views Shepard, the player character, as a Parental Substitute who will teach him how to do all the important krogan things like break stuff and set it on fire. In the Citadel DLC, after he sets a Citadel Security car on fire, steals it and crashes it, this exchange can happen:
Shepard: Grunt, apologize to the nice man for setting his car on fire.
Grunt: (looking at his feet) I'm sorry I set your car on fire...
[notices Shepard's expression]
Grunt: ...and I won't do it again.
[...and as soon as the police have left]
Shepard: I love you, Grunt.