There was an idea to have the Weyland and Tyrell corporations be merged in Prometheus, and have a bodyguard with a name referencing Roy Batty. "There’s one idea that I’m very sad that we didn’t do. Ridley, one day, came in and said, "You know, I’m thinking what if it’s the Weyland-Tyrell Corporation? Is that cool? Maybe the bodyguards, you know, that come out with Weyland, maybe one of them says Batty on his uniform. And we're like "Awesome! Do it, do it!"
A blu-ray extra for Prometheus suggested that Tyrell is Weyland's mentor. Weyland says Tyrell was on top of a pyramid, overlooking a city of angels. Tyrell worked at the top of the pyramid-shaped Tyrell Corporation set in Los Angeles. While Weyland made androids, Tyrell genetically engineered replicants and implanted them with false memories, as Weyland calls out in his letter. The person who created this text confirmed it was just a fun nod and not out-right confirmation.
As part of the 20th Anniversary Edition "Alien" DVD in 1999, a DVD extra titled "Nostromo Dossier" shows extended profiles for the crew. Dallas is shown to have once worked for the Tyrell Corporation from Blade Runner.
Ridley Scott remarks on the director's commentary for Blade Runner that they could be connected. "There’s almost like a connective tissue between all the stuff I went through on 'Alien' into the environment of the Nostromo and people living within close proximity to people who still have Earth-bound connections and here we have people on Earth, so almost this world could easily be the city that supports the crew that go out in Alien. So, in other words, when the crew of Alien come back in, they might go into this place and go into a bar off the street near where Deckard lives. That's how I thought about it." Notably, Blade Runner and Alien are set 103 years apart.
In Peter Weyland's 2023 TED Talk, he remarks that it is illegal to create robots indistinguishable from humans. In Blade Runner, Replicants were declared illegal after a NEXUS 6 mutiny in an off-world colony.
The PURGE screen from Alien was reused in Blade Runner to save time.
In Soldier, Todd's weapons training record lists the "USMC Smartgun" and "M41A pulse rifle" from Aliens, although it also references things that it isn’t in-continuity with it as well, like Star Trek and Star Wars. The film establishes the United States Colonial Marines Corps as existing. However, they did not exist in the Alien Universe until 2101.
In Blade Runner 2049, a ship similar to the Sulaco from Aliens can be seen.