The defense department’s technology wing asked the Twitterverse for help in finding privately owned underground space for testing purposes — and then made a “Stranger Things” joke amid a flurry of replies from freaked out users.

DARPA, the Defense Advanced Research Projects Agency, touched off the madness with a cryptic tweet Wednesday morning.

“Attention, city dwellers! We’re interested in identifying university-owned or commercially managed underground urban tunnels & facilities able to host research & experimentation. It’s short notice… We’re asking for responses by Aug. 30 at 5:00 PM ET.”

In a second tweet, it specified that its ideal space is “human-made underground environment spanning several city blocks w/ complex layout & multiple stories, including atriums, tunnels & stairwells.”

Twitter users pondered the government’s intentions — as DARPA takes credit for creating the internet itself, has put $2 billion into developing artificial intelligence and has created several military stealth and missile systems.

A spokesman for the agency told Gizmodo, “DARPA is interested in exploring this domain for researchers to analyze and enhance approaches to improve situational awareness and response times in emergency scenarios,” which did not quell suspicion.

“This is both exciting and ominous,” one user wrote, prompting a DARPA response, “Even to us.”

Another user sarcastically tweeted, “‘We are definitely not looking for new places to keep the Demogorgons” — referencing the demons from the Netflix show “Stranger Things.”

DARPA tweeted back, “Please. Demogorgons are such a Department of Energy thing.”

DARPA has confirmed via Twitter that the space will be “partially aimed” at helping its “Subterranean Challenge,” a civilian effort that pits teams of innovators against one another to change the way humans work underground to “enable and exploit the capability to conduct rapid and autonomous subterranean missions and saving lives through enhanced situational awareness.”

The agency added in a statement to Gizmodo:

“Complex urban underground infrastructure can present significant challenges for situational awareness in time-sensitive scenarios, such as active combat operations or disaster response. DARPA is interested in exploring this domain for researchers to analyze and enhance approaches to improve situational awareness and response times in emergency scenarios,” the DARPA spokesperson continued. “Locations submitted could help the research community identify relevant sites for further field experimentation to accelerate their development of such technologies.”