Barnabas T. Bullion, sometimes nicknamed Barney, was a human man.
A sometimes bull-headed, but not truly villainous, mining entrepreneur in the Gold Rush-era Big Thunder Mountain area, in Arizona, having taken the claim over from the deceased Henry Ravenswood of next town over, Barnabas T. Bullion was also the father of the equally stubborn, adventurous Abigail Bullion.
A member of the Society of Explorers and Adventurers, he ignored the warnings of his fellow members Jason Chandler and Madame Zarkov about digging too deep into the Mountain, and ended up accidentally rousing the mystical force known as the Thunderbird, who threatened to end him and his mine in revenge for his callous treatment both of the site and of his employees (whom he let his foreman George Willikers mercilessly abuse). With help from his daughter, however, Bullion was able to make amends, and gave up on the mine, which remained abandoned.
It would seem that Bullion had taken a trip down the Colorado River in 1870, contributing a paddle from the expedition to The Tropical Hideaway's wall of paddles, as is the S.E.A. tradition.
Behind the scenes
Barnabas T. Bullion was added to the backstory of Walt Disney World's Big Thunder Mountain Railroad attraction through the 2013 expansions to its queue. The portrait of the character was designed after Imagineer Tony Baxter, a major contributor to the creation of the Big Thunder Mountain Railroad attraction.
Part of the unfolding Society of Explorers and Adventurers megatheme created in the 2010's in the various Disneylands, Bullion therefore makes cameos in other attractions tied to it, on top of his appearance in the Big Thunder Mountain Railroad comic from 2015, when the character was given a redemption arc at the request of Tony Baxter himself.