The last place you'd expect to see a Marvel/DC crossover is in the pages of a comic that centers around the exploits of the Inhumans' teleporting dog, Lockjaw. But the world of superheroes is full of surprises, and that's exactly where said crossover takes place.
On page 17 of Lockjaw #4 (released yesterday), by writer Daniel Kibblesmith (perfect surname when you're writing about a powerful canine) and artist Carlos Villa, the Inhuman companion battles Annihilus, the dude in charge of the Negative Zone. Their conflict takes them to different places like Duckworld (home of Howard the Duck) and, more shockingly, the DC Universe.
Each location they travel to gets a little title in the left-hand corner, except this one, which simply reads "[REDACTED]". More importantly, we see the bottom halves of Superman and Wonder Woman, who say, "Uh, pardon us, friends" and "This is private property," respectively. The whole thing is just one little panel, but it's enough to blow your mind and wonder how this came about in the first place.
The Lockjaw solo series kicked off in February with the titular character learning about "his long-lost littermates" and teaming up with D-Man (Dennis Dunphy) to save them. However, this isn't the first time the Inhumans' best friend has had his own comic run, believe it or not. In the 2009 limited series Lockjaw and the Pet Avengers, he joined up with a bunch of superhero-themed animals to track down Infinity Stones.
This also isn't the first time the publishers have made passing references to one another's universes. Over the years, Thor has bumped into Clark Kent at S.H.I.E.L.D. headquarters (1966), Hulk fought Doomsday (1994), Green Lantern received directions from Doctor Strange's manservant Wong (also 1994), and a "Deadpool-y" version of Deathstroke meets Batman and Superman (2006).