Though his pro-wrestling "stage accent" may have seemed unintelligent, he spoke with a degree of consideration and eloquence that suggested a greater intellect beneath his bombastic wrestler demeanor. Part of his unique pattern included always referring to himself in the third person and frequently employing earth-related puns, such as "The Boulder is going to win this in a landslide!"
When The Boulder was a combatant in the Earth Rumble VI tournament in 100 AG, he faced The Big Bad Hippo in the first round. After taunting his opponent, The Boulder commenced with a frontal attack by chucking large pieces of rock at The Hippo, who remained unfazed by the assault. Almost knocked out of the ring by The Hippo's unique "rocking the boat"-technique, The Boulder managed to defeat The Hippo by lifting the earth underneath his feet and tossing him out of the arena. This feat of power sparked Katara and Aang's attention, who were spectators of the tournament in search of an earthbending teacher for Aang. Katara commented that The Boulder had some good moves, a statement to which Aang rightfully retorted that The Boulder was more prone to listen to his muscles than anything else.
As the tournament proceeded, The Boulder did what he did best and entertained Sokka and the other spectators by defeating all the other contestants with extravagant moves, progressing easily to the final round of the competition where he met the Blind Bandit. When the Blind Bandit entered the ring, The Boulder announced that he felt conflicted about fighting a young blind girl. However, he declared his conflicted feelings at an end after the Blind Bandit accused him of being scared and threatened to bury her in a "rock-a-lanche". The Blind Bandit challenged The Boulder to attack her, mocking his stage name by calling him "The Pebble". As part of her fighting strategy, the Blind Bandit waited and listened for The Boulder to make the first move. As The Boulder got ready to stomp the ground, the Blind Bandit made her move by sending an earth fissure at him, forcing him to do a painful split. He was subsequently thrown out of the ring with ease, effectively losing the match.
When Aang accidentally defeated the Blind Bandit with his airbending, The Boulder told Xin Fu that he suspected that Aang and the Blind Bandit had worked together to scam the rumble's host and split the reward. When the latter set out to recollect his prize money, The Boulder and the other Earth Rumble VI contestants helped him in this endeavor and kidnapped both the Blind Bandit, also known as Toph, and Aang. In order to ransom them back, The Boulder and Xin Fu left a note asking for five hundred gold pieces.
When Toph's parents paid the ransom to successfully free their daughter, Sokka and Katara wanted to free Aang as well, but were thwarted in their attempt by the band of wrestlers, who wanted to collect the bounty from the Fire Nation for capturing the Avatar. However, as they left the ring, Toph challenged The Boulder and the other fighters, threatening to beat them all again in an earthbending battle in case they refused to release Aang, a comment to which The Boulder took issue. Engulfing the arena in a dust cloud, Toph engaged in a battle with all the wrestlers at once and managed to successfully take out every single one of them. At one point, The Boulder, alongside The Hippo and the Headhunter, confronted Toph. Tag teaming, the three fighters charged at the blind earthbending girl. However, by shifting the ground on which they all stood, Toph was able to defeat them with ease, knocking them out cold.
The Boulder reappeared months later on the day of the invasion of the Fire Nation, alongside The Hippo and many other earthbenders. He stated to Toph that he and The Hippo no longer fought for others' entertainment, but for the good of the Earth Kingdom. During the invasion, The Boulder proved to be a true asset to the invasion force, as he managed to take down several battlements. Ultimately, the plan failed, and The Boulder, along with the other adults from the invasion force, was captured by Fire Nation forces and sent to prison.
The Boulder was actually quite bright, although this intelligence was often belied by his bombastic stage persona. He was a determined earthbender who seemed somewhat arrogant, referring to himself in third person, basking in the praise of his fans and, as Aang put it, "listening to his big muscles". However, when it came time for the invasion, it was revealed that he had a great sense of nationalism and patriotic duty to his nation, which contrasted with his earlier attitude in the tournament ring.
The Boulder was one of the best earthbending fighters in the Earth Rumble VI tournament. While his style of fighting was less extravagant than the other fighters, he defeated them handily. His straightforward, powerful earthbending skills were effective in their simplicity. However, he was still no match for Toph, who easily defeated him in the final round of the competition with only two moves.
According to Toph's ransom letter, The Boulder's name was written as 大石塊 which translates as "big chunk of rock".
The Boulder was an illeist, referring to himself in third person, such as, "The Boulder is going to win this in a landslide!" He only referred to himself in the first person three times, twice while talking to Xin Fu and once to Toph prior to the invasion of the Fire Nation.
The Boulder was inspired by real life pro wrestler Dwayne Johnson, also known as "The Rock", who, like The Boulder, refers to himself in the third person when he speaks. According to the Avatar Extras for "The Blind Bandit", the production team tried to get Dwayne Johnson to voice The Boulder, but they were unable to do so, and he was eventually voiced by pro-wrestler Mick Foley, a good friend of The Rock.
He bore a resemblance to Sud, Roku's earthbending teacher, who was modeled after an early design of Toph.