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. They also loved going fishing together.
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, mischievous, 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.
Otis can sometimes be a bit arrogant and overconfident. 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.
Otis is a white cow with black spots, blue eyes, a light pink snout and lips, and udders that produce milk (despite being a male).
Once, after getting milked by attaching the machine to his udder, he became extremely skinny because his body was drained of all its milk content.
Otis' pink udder is a prominent feature of his large body, It is round and quite fat and has four nipples that milk can be squeezed out of.
Among his many disguises in Back at the Barnyard are newscaster Gill O'Malley (in "The Big Barnyard Broadcast" and "Anchor Cow"), politician Ned Bovine (in "Otis for Mayor"), golfer Heifer Woods (punning off Tiger Woods in "Cowdyshack"), real estate agent Dick Human (in "Buyers Beware"), or Bob Notacow (in "Bling My Barn"). Otis has a superhero alter-ego as Cowman. Once, he has even gone as far as to dress in drag as a female to prove that girls have it easy in the episode "Some Like It Snotty."
- Despite being biologically male, Otis has an udder like the other male cows. In reality, only female cows have udders, not bulls. The reason all the male cows were designed like this in the franchise is because Steve Oedekerk figured that city folk thought that all cows would look like this.
- Otis can make milk from his udder, which can be used for drinking and attack purposes. As well, it is an alien weakness.
- In the film, Otis cannot produce milk, but in the series, he can lactate efficiently from his udder. This could be due to the fact that his udder and milk producing equipment had not developed fully yet.
- Otis is the farmer's top milking cow.
- Even though Otis produces the most milk on the farm, he has a very sensitive udder, and hates cold hands and milk machines.
- Otis sometimes forgets how to spell his name.
- Otis is nicknamed Oaty by Maddy.
- Otis and Pig have cameos in the pilot episode of Planet Sheen.