5 times when a UFC fighter called out an opponent from a different weight class

#2. B.J. Penn – former UFC lightweight champion

BJ Penn famously called out Georges St-Pierre in the summer of 2008, but the fight did not go well for him

When B.J. Penn defeated Joe Stevenson to win the vacant UFC lightweight title in early 2008 and then destroyed former champion Sean Sherk in his first defense, it felt like the Hawaiian had finally reached his full potential in the octagon.

Unlike the unfocused ‘Prodigy’ who had drifted around in different weight classes, this Penn was lean, mean and seemed unstoppable. Fans across the world wondered if any 155lber could stop him. Naturally, in his mind, the Hawaiian had bigger fish to fry.

So three months after his win over Sherk, Penn burst into the octagon after Georges St-Pierre’s dominant welterweight title defense against Jon Fitch, intent on challenging the Canadian to a champion vs. champion bout.

While the callout came off as a little corny – Penn yelling “let’s do this!” in a high-pitched voice – it definitely worked, drumming up plenty of interest for a potential fight between the two.

Of course, the fact that ‘The Prodigy’ had already fought GSP once, with the fight ending in a controversial decision in favor of the Canadian, definitely helped matters. Despite St-Pierre having more deserving contenders waiting in the wings, the UFC unsurprisingly granted Penn’s callout and signed the bout.

Unfortunately for the Hawaiian, the fight went terribly for him as he suffered a horrific beatdown en route to a fourth-round stoppage. The promotion would have to wait another seven years for their first double champion and Penn duly returned to the lightweight division.

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#1. Nate Diaz – UFC welterweight contender

Nate Diaz's call-out of the smaller Conor McGregor is probably the most famous in UFC history

While some fans criticized Colby Covington’s recent callout of Dustin Poirier, feeling that no fighter should really challenge a foe in a lower weight division, it’s easy to forget that arguably the most famous callout in UFC history featured just that.

The callout in question, of course, saw Nate Diaz, who competed as a lightweight at the time, call out then-featherweight kingpin Conor McGregor in an impromptu, sweary rant that instantly went viral across the world.

According to Diaz, McGregor was “taking everything he’d worked for.” While at that point, it felt like a fight between the two was simply a pipe dream, the callout had a huge effect on both the UFC’s fanbase and its matchmakers.

Sure enough, just three months later, when McGregor’s planned lightweight title challenge against Rafael dos Anjos fell through thanks to the Brazilian suffering a broken foot, the promotion swiftly turned to Diaz to replace him.

Evidently, ‘The Notorious’ cared as little for the boundaries of weight classes as Diaz did, as he agreed to fight the Stockton-based fighter at 170pounds. That was 25 pounds heavier than he’d ever competed at in the octagon before.

The rest, of course, is history. Diaz stunned everyone by choking out McGregor in the second round of their clash. The pay-per-view drew well over a million buys, resulting in the UFC booking an instant rematch that the Irishman won via decision.

Six years on, fans are still waiting for a potential trilogy bout between the two, making it one of the most highly-anticipated fights in MMA history. That's not bad considering the rivalry began with an unorthodox callout of a fighter in a lower weight class!