Bender was always careless robot, until he flushed Nibbler down the toilet.

Leela was crying and sobbing over Nibbler, but Bender didn't cared.

Professor Farnsworth decided to re-program him with emotions, only to try how Leela was feeling.

Bender stared to feel guilt and went to return Nibbler back to Leela.

Professor made you re-program Bender back into himself careless. you sat on Bender's lap so you could reach the programing device in his head, that was sitting next to him.