The character known as Ataru's Father is a quintessential representation of the overworked and underappreciated Japanese salaryman, whose life has been turned into a financial and domestic nightmare by the antics of his son. His personal name is never revealed within the series, and he is almost always seen in a traditional yukata when at home, a stark contrast to the business suit he likely wears for his office job. His daily existence is dominated by two things: his job as the family's sole provider and the endless, crushing worry over his mortgage, a burden made infinitely worse by the fact that his home is a frequent casualty of the chaos brought on by Ataru and the alien Lum.

In terms of personality, Ataru's Father is defined by his timidity, resignation, and a quiet, almost desperate desire for a normal, peaceful life. He is not a man of action or confrontation. Instead of intervening in the latest supernatural or extraterrestrial crisis unfolding in his living room, his typical response is to seek refuge behind his newspaper, hoping the insanity will simply pass him by. He is a classic Extreme Doormat and Useless Bystander Parent, possessing very little dignity and often lamenting his lack of respect as the family's breadwinner. His emotional range primarily swings between exasperation, whining, and a deep, soul-crushing anxiety about money, frequently crying out over the cost of repairs or the number of payments left on the house.

His primary motivation is survival, both financial and emotional. He continues to work his dead-end job and make endless loan payments to keep a roof over his family's head, even as that roof is repeatedly blown off. He and his wife share a common, often rocky domestic relationship, occasionally reminiscing about their younger days as newlyweds and the daughter they had hoped for, only to end up with Ataru. They genuinely care for their son despite their constant verbal abuse, becoming genuinely upset at the prospect of his death. However, they openly adore Lum as the daughter they never had, showering her with a level of affection they have never shown Ataru, much to his chagrin.

Within the story's framework, Ataru's Father serves as a grounding, if tragic, element of normalcy. He represents the mundane, everyday world that is constantly being disrupted by the extraordinary. His lamentations over the mortgage are a recurring gag that highlights the real-world, financial consequences of the series' fantastical conflicts. While he is not a driver of the plot, he has moments of minor development. In a notable episode, he overcomes his initial wariness of Lum's father—a giant, intimidating alien—and begins to look up to him as a role model of "manly living," a quiet moment of reflection that adds a layer of depth to his otherwise beleaguered character. He possesses no special abilities or fighting skills; his only notable "skill" is his capacity for silent endurance and his remarkable ability to continue paying off a mortgage on a house that is destroyed with alarming frequency.