Bender, the maniacal but loveable robot rogue from Futurama, is somewhat defined by his openly malicious side. However, every once in a while, something would appear in his life that revealed a surprisingly sweet aspect of his nature. Across two separate seasons, this is seen when he's twice confronted by the possibility of fathership. In Season 5 of Futurama, Bender's shown to be the worst father possible to his first-born son, but the character would embrace being a dad in a surprisingly heartfelt way in Season 7.
The first time Bender is shown with a child is a hilariously dark sequence from the show's fifth season, originally released as a series of direct-to-video movies. In "The Beast With A Billion Backs," Bender finds himself enraged with humanity and leading the League of Robots -- an Illuminati-esque alliance of robots from across the world.
To fully gain control of the world, Bender must turn to the Robot Devil to supply him an army. The Robot Devil agrees, on the condition that Bender surrenders his first son. While this leaves the Robot Devil laughing maliciously, Bender casually stands up and excuses him from the room to find Bender Jr. in suburbia.
A seemingly innocent young robot, Bender Jr. rushes forward when he sees his father and embraces him in a hug. He even exclaims how he always knew Bender would come back for him someday. However, Bender immediately brings his son to Robot Hell and punts him out the window, leaving him to land in a pit of lava. It's an incredibly dark moment that's contrasted hysterically by Bender's complete lack of concern for his son. Notably, this casually cruel act by Bender is all in service of being reunited with his best friend, Fry, who spends much of "Beast With A Billion Backs" away from Bender.
Bender has far deeper feelings for his second son, Ben, who plays a central role in Season 7, Episode 1, "The Bots and the Bees." After having a one-night-stand with Planet Express's new soda machine, Bev, Bender is surprised when he discovers the pair have conceived a son. Bev quickly runs out on them, leaving Bender to raise his quickly growing son.
The two actually bond well, becoming inseparable in no time at all. Ben's only real regret is that he didn't possess the ability to become a Bending Robot like his father before him. Eventually, Bender learns about a way to install the necessary programming into his son -- albeit at the cost of any memory of who Bender really is.
Deciding his son's happiness is more important than his own, Bender reluctantly agrees to the procedure, allowing Ben to go to college, become a Bending Unit and leave Bender's life. Bender's connection with his son, coming at the beginning of the show's final year, can be seen as the ultimate display of how Bender grew as a character.
While he at times could be unfeeling and obnoxiously petty, Bender also defines himself by his friendships. Over the course of the show, he finds ways to forge connections with others, more or less gaining a family in the form of Planet Express. While he may not have ever known his first son and only saw him as a means to an end, Bender raises Ben directly and becomes the kind of father that Leela could consistently compliment and admire. Bender becoming a good father is one of his most unexpected turns, but it's an incredibly fitting role for him to take on, especially after the amount of depth the character displays over the course of the series.