Rhino (real name being Alexander "Alex" O'Hirn) is one of Spider-Man's toughest opponents. In Ultimate Spider-Man, he is a Midtown High School student turned rhinoceros mutant.
Rhino was created by Stan Lee and John Romita Sr.
Spider-Man and Power Man encounter Rhino at the burning Oscorp building and end up rammed into a tree by Rhino who makes off with some exotic animal-related chemicals. Spider-Man and Power Man later stakeout another Oscorp building and find Rhino charging toward an Oscorp train. Spider-Man and Power Man fight Rhino with the resulting fight causing Rhino to gash Power Man's leg. As Rhino charges toward Spider-Man, S.H.I.E.L.D. arrives causing Rhino to retreat with his "medicines." The next day, Peter Parker anticipates that Alex is responsible as Spider-Man sees Alex drink a chemical that transforms him into Rhino.
Spider-Man fights Rhino to keep him from attacking Flash Thompson while trying to reason with him. Spider-Man then works to protect Flash Thompson and not even Spider-Man's electro-webs could phase Rhino. When Spider-Man finds Flash Thompson at his house near a gas station, Spider-Man gets Flash Thompson away from the gas station when Rhino causes it to explode. Spider-Man tells Flash Thompson to call for help as he continues to fight Rhino. When Rhino starts charging toward Flash Thompson, Spider-Man tries to reason with Rhino while doing a bucking bronco move on him. In the nick of time, Power Man arrives and grabs Rhino by the horn. Spider-Man tells Flash that Rhino is actually Alex. Spider-Man traps Rhino on some oil as Spider-Man and Power Man double-team on Rhino enough to regress back to Alex O'Hirn.
As Alex is arrested by S.H.I.E.L.D., Flash Thompson apologizes to Alex as a female S.H.I.E.L.D. agent tells Flash that they'll take care of Alex.
He was later turned back into the rhino juice-seeking Rhino by Octavius to be part of the Sinister Six in exchange for more serum and he fought Power Man, but was defeated by Nova and placed in a cell in S.H.I.E.L.D.'s new headquarters.
Rhino is sprung out of Ryker's Island and is equipped with a tank-like armor. With the Sinister Six armored and reassembled, Rhino fights Spider-Man and then Power Man once again. He also assists in the group's gang assault on Iron Patriot. During all the chaos, Rhino ends up defeated along with the other Sinister Six members.
After the Green Goblin's rampage, Spider-Man was able to defeat Rhino along with the other Sinister Six members.
In "Rampaging Rhino", Dr. Connors tells Spider-Man that Rhino is unable to become Alex O'Hirn again after running an analysis on him. Flash (who has since reformed and become "Agent Venom") and Rhino continue their old rivalry when Rhino escapes from the Tri-Carrier. With help from the Hulk and his newly upgraded Iron Spider Hulkbuster armor, Spider-Man temporary subdues Rhino in a tunnel after a long destructive fight across the city. However Rhino gets back up to attack Hulk. Spider-Man and Hulk then reason with Alex on a human level which leads to Spider-Man, Hulk, and Rhino working to keep the tunnel from collapsing. Upon making it to Queens, Rhino was unable to have the courage to go into his house and turns himself over to the S.H.I.E.L.D. Agents. With the help of Hulk, Spider-Man persuaded Nick Fury to let Rhino try out as a student at the S.H.I.E.L.D. Academy. Fury agrees to the terms while holding Spider-Man responsible for Rhino's actions.
In the episode "Ant-Man", Rhino continued his educated at the S.H.I.E.L.D. Academy, he took part in a lesson taught by Ant-Man. When Doctor Octopus escaped from his cell, he helped Nova, Dagger, and Agent Venom battle him.
At the end of the episode "Lizards", Rhino is revealed to be a spy for Doctor Octopus, as he was the one to inject Dr. Connors with the Lizard serum and escapes with Doctor Octopus with Agent Venom.
In the episode "Double Agent Venom", it is revealed that Rhino worked with Doctor Octopus so that he can restore him to Alex O'Hirn. When Spider-Man and Scarlet Spider arrived to free Flash Thompson after he was separated from the Venom symbiote, Rhino buys them time to escape. Following Kraven the Hunter's defeat and Spider-Man's group escaping, Doctor Octopus plans to cure Rhino of his loyalty problem.
In the episode "The New Sinister 6" Pt. 1, Rhino appears as a member of Doctor Octopus' Sinister Six at the time when they attack the Triskelion. During the fight, it was shown that Rhino was made obedient to Doctor Octopus as he claims that someone else was the spy. He was subdued by Squirrel Girl's squirrels.
In the final episode, Rhino become human again.