In his youth, Otis lost his biological mother at a county fair when he was a calf. It is unknown what happened to his biological father, but he presumably died of an illness. Afterwards, Otis was adopted by Ben and lived a happy, normal life with him as father and son.
When he was young, Otis was constantly bullied by Krauser Krebs, who would beat him up and squeeze the milk out of his udders. At one point, he had a best friend named Eddie who stole his idea for a product. Afterwards, Otis grew up and made friends with the other animals of the Barnyard.
In the film, Otis loses Ben when Dag kills him outside the chicken coop. Devastated and depressed, Otis blames himself for his father's death since he wasn't there for him (which even Dag harangues him for). In the end, Otis is elected the new leader of the Barnyard, defeats Dag and the coyotes, and becomes a father to Daisy's newborn son Lil' Ben (whom he named after his father).
Otis is an intelligent, fun-loving, friendly, energetic, happy-go-lucky, goofy, carefree, kindhearted, brave, determined, adventurous cow who knows how to work guitars, cell phones, and microphones. Instead of having strict, serious rules, he would rather have fun with his best friends and mess around all he wants and not take responsibilities.
Otis is glad to face his fears to save himself and his best friends; however, when it comes to money, Otis is usually selfish, greedy, and stubborn and stingily keeps it all to himself. Despite this, he is genuinely a nice, caring cow with a bovine heart of gold.
He enjoys hanging out and having fun with his best friends. He also likes to pull tricks on the Beadys and the Farmer.
In the film, Otis has a somewhat rebellious, stubborn "big man on campus" nature with Ben and deliberately ignores him when he tells him to grow up and become more responsible instead of goofing off since he will become the leader of the Barnyard someday when Ben passes away.
After Ben gets murdered by Dag that night, Otis witnesses his father dying in his hooves and becomes extremely depressed and not as outgoing, devastated by the incident. Later, Otis is elected the new leader of the Barnyard, despite him blaming himself for Ben's death and dwelling on it as he strongly feels that he should have been there for him instead of partying with the animals in the Night Barn.
Towards the end of the film, Otis avenges his father by bravely defeating Dag in the junkyard while protecting and rescuing the captured hens and Maddy (though he got bitten in the leg by Dag at one point, similar to Ben). Upon arriving back home, Otis eventually becomes a loving husband to Daisy and a father to his newborn son Lil' Ben (whom he and Daisy had named after his late father). Slowly, he starts to mature as a more responsible leader, husband, and father.
When Daisy left the Barnyard in Back at the Barnyard and was replaced by Abby, it is unknown if Otis was reluctant about falling in love with Abby since he had Daisy and Lil' Ben before.
Otis can sometimes be a bit arrogant. He is also rather gullible as in the Back at the Barnyard episode "Abby & Veronica," while playing ball with Abby, when she fake-panics and asks Otis if there is a scorpion on a nearby tree while pointing at it, Otis immediately believes her words and freaks out and thus, loses the game by getting hit by Abby's ball.