Instead, what fans saw on Saturday night's pay-per-view broadcast was the result of a bet that Hallman had with fellow fighters Len Bentley and Sterling Ford. In case you couldn't tell, Hallman did not come out on the winning end of that wager.
"I won't say what the bet was about, but I lost a bet to those guys and losing the bet meant that I got to wear some speedos," Hallman told Helwani.
"I thought it was funny," he added later. "I thought it was embarrassing for me. Obviously, that's why I had to do it. But I didn't think anybody would be cross about it."
One man who was displeased was Hallman's boss, UFC president Dana White, who said he was "horrified" and "disgusted" by Hallman's shorts, and vowed that no fighter would ever again be allowed to wear something like that into the cage.
But as upset as White seemed after the fight, Hallman remains convinced that his job security has more to do with his fighting ability than his attire, especially since he took on Brian Ebersole in Philadelphia even after sustaining an elbow injury two days before the fight.
"I don't think they're going to fire you over something like that," Hallman said. "I mean, he knows I went in there and fought injured because I didn't want to screw up their card. You can't fire somebody for doing something that's not illegal or not wrong. You can say, don't do it again. But it wouldn't be right to be like, okay, you wore legal trunks but I didn't like them so I'm going to fire you. Dana's not like that. He might say, if you do it again I'll fire you, but he's not going to fire someone for wearing trunks that were legal."
As for the elbow, which Hallman said he was currently on his way to a specialist about, he still doesn't know what caused it to swell up on the Thursday before the fight.
"That's the mystery," he said, adding that he sought medical attention on Thursday, but "again Friday, after the weight cut, it blew up again. Same thing, we tried to treat it, and then Saturday...my arm was swollen up huge and I couldn't move it."
Esther Lin, MMA Fighting" data-gallery-title="UFC 133 Fight Night Photos" data-gallery-id="2912258" >
Esther Lin, MMA Fighting" data-gallery-title="UFC 133 Fight Night Photos" data-gallery-id="2912260" >
By the time he stepped in to fight Ebersole, Hallman said he had very little use of his right arm, which he believes left him unable to capitalize after taking Ebersole's back early in the fight. Hallman said he doesn't know how long the arm injury will keep him out of action, but what he'd really like is a rematch with Ebersole once he's healthy.
As for the speedos, losing that particular bet was costly in more ways than one, since it only left him room for two sponsors. It also provoked a strong, though mixed reaction from fans, Hallman said.
"I had about 400 Twitter mentions. About 70 percent of them were pissed off about the shorts, and the other 30 percent, mostly women, were complimenting the choice of shorts."
Still, after White personally told him that his shorts would be "effing illegal" from that point on, it doesn't seem as though any other fighter will be making similar bets in the future. In Hallman's mind, at least, it succeeded in at least one respect.
"How many guys who lost a fight are on your show the day after? Not very many, so I think it probably worked out a little bit better," he told Helwani. "Maybe I can put those speedos on Ebay as the last speedos ever worn in the UFC and make some money."