It may come as a surprise that Deadpool has a seemingly foolproof method of detecting evil Marvel variants, and it's straight out of Star Trek. When his mission is yet again to terminate the X-Man Cable, Wade Wilson discovers his former friend and wannabe savior of the world has disappeared, possibly to another dimension altogether. With the X-Men's help, Deadpool uses his unique connection to Cable to track him down, ending up in the Age of Apocalypse reality. Facing evil variants of familiar Marvel heroes or villains, Deadpool reveals his decision making relies on if they're sporting an "evil goatee", a sign of diabolical doppelgangers that was originally made famous in Star Trek.
When Wade is manipulated by the curious techno-villain Black Box to destroy the greatest threat to mankind, he teleports to the floating city of Providence, looking for its powerful founder, protector, and leader. Deadpool quickly learns that Cable isn't there, a fact confirmed by concerned members of the X-Men. Following his disappearance after a mission with X-Force, the X-Men compose a plan that despite their better judgment hinges on Deadpool's cooperation. Using advanced machines created by Forge, they're able to tap into Deadpool's unique biological connection with Cable and discover he's traveled to other parallel dimensions during his absence.
In Cable and Deadpool #15 by Fabian Nicieza, Patrick Zircher, M3th, Gotham, and Cory Petit, Deadpool gets tired of all the technobabble and explanation of the plan and chooses to teleport away, the X-Men secretly monitoring his progress and prepare to assist him if necessary. Wade ends up in the nightmarish and desolate Age of Apocalypse, a popular Marvel parallel dimension where Apocalypse reigned supreme without the existence and later opposition of Charles Xavier. Upon his arrival, Wade is attacked by three of Apocalypses' Horsemen, facing similar yet malevolent versions of Archangel, the Blob and Spider-Man. Although Wade's commentary reigns supreme, he is easily beaten and subdued by the Horsemen, his defeat interrupted by the intervention of X-Men's Cannonball and Siryn. When Theresa moves to free Deadpool, Wade questions which version of Siryn she is, leaning more toward good because she isn't "sporting the mirror universe-mandated "evil goatee."
This concept originally appeared in Star Trek Season 2, Episode 4 "Mirror, Mirror" where Captain Kirk and members of his crew accidentally end up on the Enterprise of a parallel dimension that operates as the direct opposite of their universe. Among those significant changes was First Officer Spock sporting a mustache and goatee along with his willingness to inflict pain or even murder others. The episode's popularity caused the "Mirror Universe" to return in Star Trek: Deep Space Nine and Star Trek: Discovery but also was the subject of humorous parodies for shows like South Park or Community. Although the Age of Apocalypse Spider-Man did have a little more facial hair than usual, the reference is another case of Deadpool's pop culture references poking fun at the extraordinary circumstances while also logically addressing suspicion of familiar faces in another dimension.
Although Deadpool was initially suspicious, Siryn uses her knowledge of Deadpool from their former romance in years past to prove that she's not the Age of Apocalypse variant which gets another chuckle from the audience. Although Deadpool and his X-Buddies soon learn who the Fourth Horsemen of the Apocalypse was, its hilarious to see that Deadpool relies on Star Trek to shape his understanding of the multiverse and how to ascertain the good from the bad variants, something that isn't very logical indeed.