DC Comics created a clear rip-off of Marvel's Deadpool character in its Deathstroke comic, and then had the character not just repeat some of Wade Wilson's most famous dialogue, but also speculate about Marvel's right to sue.
For as long as Deadpool has existed, Marvel and DC fans alike have speculated that he's a particularly unsubtle rip-off of DC's Deathstroke. Deadpool first appeared in The New Mutants #98 (created by Rob Liefeld and Fabian Nicieza), and like Deathstroke was an acrobatic, sword- and gun-wielding assassin in a two-tone costume. Even Deadpool's real name, Wade Wilson, suggested comparisons to DC's Deathstroke, aka Slade Wilson. The comparison has remained a talking point for comic fans over the years, but in Deathstroke #36, Christopher Priest and Fernando Pasarin decided to flip the script.
In the story arc "Deathstroke: Arkham," Deathstroke is confined to Arkham Asylum after what he believed to be a hologram of his ally William Randolph Wintergreen is seemingly revealed to be a hallucination. There, he meets other patients through group therapy, managing to antagonize some of Gotham's most dangerous criminals. One of the only people Deathstroke doesn't quickly turn into an enemy is a young man named Devon, who claims that an alien race known as the Pulorians are preparing to attack Earth. While he's been working to stop them, the nature of the Zeta Beam technology which transports him across the universe means that despite being gone for long stretches of time, he returns only moments after disappearing, leading the authorities to brand his warnings as delusions.
Of course, Devon is telling the truth, and recruits Deathstroke to fight off the invasion force, helped by an army of villains who reluctantly address a problem none of the superheroes believe exists. Over the course of the adventure, Devon is inspired by Deathstroke, taking up his own identity as Death Masque. The identity is a very clear parody of Deadpool. Death Masque's entire look is patterned after Marvel's Merc with a Mouth, and so is his dialogue. At one point, he even says, "I know the key to the universe, Mr. Liefold! You see... There is a man... with a type-writer..."
"There is a man. At a typewriter," was first spoken by Wade in Deadpool #34, marking the earnest decision to make Wade canonically aware of the fact he's a fictional character, and becoming a common refrain for the antihero ever since. Amusingly, the writer on this issue was Christopher Priest (with art by Paco Diaz), meaning that Priest is actually referencing his own work on Deadpool through his writing on Deathstroke. Having spoken the famous line, the action of the comic panel pauses, and Death Masque looks to the reader and says, "All right, let's admit... It would be freaking ironic if they sued us." It's clear from implication that the "they" in question is Marvel, and the point of Death Masque is to play off the idea that Deadpool is a Deathstroke rip-off by blatantly ripping him off in return.
"Deathstroke: Arkham" isn't even the first time DC has done this. In Superman/Batman Annual #1 (by Joe Kelly, Ed McGuinness, Ryan Ottley, Sean Murphy, and Carlo Barberi), the titular heroes accidentally cross over into Earth-3, meeting a heroic version of Deathstroke who is once again designed after - and speaks in the comical style of - Deadpool, though the character is badly injured whenever he tries to reveal his codename. Such jokes are likely to continue as long as Deadpool is so much more famous than Deathstroke, and writers find ways to play around with what some see as a creative injustice, and others as just another amusing battleground in Marvel and DC's longheld rivalry.