Robert Pataki, known better by his nickname "Big Bob", is indeed big; he looks like he was at one point muscular, but has let himself go and started becoming slightly overweight. He boasts the same eyes, ears, nose, and unibrow as his daughter, Helga. He has gray hair, combed to the left side. Most of the time, he wears a short sleeve green golf shirt with a golden crown on the left side by the chest. He wears dark brown pants and a large, white belt.
Bob's hair is brown only for Hey Arnold! The Movie. In Hey Arnold! The Jungle Movie, Bob seems to have started balding, and now wears white shoes instead of black.
Bob is very neglectful and inattentive, and seems to put much of his attention in his business and his image as the "Beeper King". He is also extremely competitive and often takes his competitiveness too far, often making angry remarks toward his competitors. Because his oldest daughter, Olga, is a multi-talented achiever, he shows an apparent favoritism towards her, while he often ignores his younger daughter, Helga, and often forgets her name, calling her Olga time and time again.
Bob has a very short temper and seems very hostile, such as when he ran through poison ivy on a camping trip. His two catchphrases are saying "Hey... Hey-Hey-Hey-Hey-Hey!", which Helga has adopted, and "criminy" which has also been picked up by Helga. He is a huge blowhard, and serves as the antagonist to Arnold and his friends or family in several episodes. However, despite his self-centered personality, it is shown on several occasions that he does actually care about others, including Helga and other kids, and somewhere within is a conscience and a big heart. Later in "Big Bob's Crisis", Big Bob appears to finally have redeemed himself after having a heart attack. Big Bob then promises himself and everyone else that he will try to be nicer to other people other than himself.
Bob founded and owns a pager store called Big Bob's Beepers, which is his primary source of income. He seems to be knowledgeable of electronics (as seen in Hey Arnold! The Movie, when he recognizes the materials to be used for an explosive), and might have another small business selling high-tech camping equipment ("Roughin' It").
Since Miriam was supposedly born in 1952, it is safe to assume that Bob is close to the same age, putting his age somewhere around 45-50 during the series' original run.
Bob seems to have once worked as a truck driver, and claims he encountered aliens during one of his travels.
While never actually mentioned in the series, Bob might have had some sort of military experience, and he has a soldier outfit.
Bob seems to have lost interest in his wife Miriam. Their marriage is extremely dysfunctional, with their lack of communication and Miriam's apparent alcoholism. It is not known if the relationship between Miriam and Bob was ever exuberant, but it is hinted that Miriam gave up her life to marry Bob, who she thought was a great guy, but was proven wrong in the long run ("Olga Gets Engaged"). However, the two do care about each other, and whenever Olga comes home, they seem much happier and act more lovingly toward each other.
By far, out of the nuclear Pataki family, Olga is Bob's favorite. Bob is always proud of Olga for her many accomplishments. He has an entire collection of all of Olga's trophies lining the walls of his den. Bob often calls Helga "Olga" by mistake.
Most of the time, Bob has no idea that his youngest daughter even exists. Bob only gets involved in Helga's life when it benefits himself, or when it has do with a competition. Despite all of this, Bob does geniunely care for Helga, and has come through for her on a few occasions.
Nick Vermicelli is Bob's associate and possibly a business adviser. He presumably works at the beeper emporium with Bob. In Hey Arnold! The Movie he and Bob engage in a violent fight after Bob finds out he tricked him into signing off 51% of his company.
- Bob was also one of the few characters of the show to be a vulgar character on a few occasions.
- In "Summer Love", Bob rips one while driving the car on the way to the beach, to which Miriam responds by opening the window and fanning the resulting smell.
- In "The Beeper Queen", Bob can be heard saying "Mother scratcher!" when he is yelling about his back hurting (which is a sugar-coating of obscene language).
- In the movie, he tells Nick Vermicelli that he will "beat the living snot out of him" for tricking him into signing the contract (which is shown to be yet another swear-word cover-up). He also says that Vermicelli and Scheck "shafted" him.
- Bob owns a large Hummer decked out with army decals. Despite this, Bob's Hummer is most likely a civilian model. It was first used in "Arnold's Halloween" to travel through Hillwood which was thought to be invaded by aliens. Since the civilian Hummer was first released in 1992 as a 1993 model, and the Halloween special first aired in 1996, it can be assumed that Bob's Hummer is a 1993-1996 model. It was mentioned again in "Arnold's Thanksgiving" when Bob was dressed up as a soldier & he was going to use it to track down Helga when she went missing. It was used a second time in The Jungle Movie.
- Bob's daily driver is a blue 1969 Lincoln Continental Mark III with vanity license plates that say "BIG BOB." The Lincoln is seen in many episodes, driven by both Bob and Miriam, and seems to be the Pataki family car. The large, powerful, and well-built luxury coupe fits Bob's personality almost perfectly.
- In "Helga and the Nanny", Big Bob mentions that he has not had potato dumplings since his "baba" last cooked them. Seeing as how "baba" is Ukrainian for "grandmother" as well as pierogi (potato dumpling) being an Eastern European dish, it can be assumed that Big Bob is of Ukrainian descent. However, Bob could have also said "papa", which is a generic term that can mean either "father" or "grandfather". Additionally, "Pataki" is a Hungarian surname, and Hungary and Ukraine share a border.
- Also in "Arnold's Halloween", and "Helga vs. Big Patty" Big Bob has commented about losing money over football games and boxing matches, indicating that he gambles on them.