What are LMDs, and why are they doing terrible things to Marvel’s heroes?

As seen in the Jan. 10 midseason premiere of “Marvel’s Agents of S.H.I.E.L.D.,” an android with artificial intelligence named Aida has become self-aware. She has replaced Agent May with another A.I. android, called in Marvel Comics parlance an LMD (“Life Model Decoy”). Hijinks are ensuing.

Life Model Decoys, as all loyal Marvel fans know, are super-sophisticated androids that can duplicate a human being right down to his or her fingerprints and retinal scans. They’ve been part of S.H.I.E.L.D. lore going back to organization’s first story in 1965, “The Man for the Job!”

That “Man” was Nick Fury, who was at the time a World War II vet, a colonel in the CIA and, uh, a white guy. (Sorry, Samuel L. Jackson!) But he already had the eye-patch, and as he took over as director of S.H.I.E.L.D. he watched with his one good peeper as no fewer than four Nick Fury LMDs got assassinated by Hydra. That’s why they call ’em “decoys,” folks!

So right from the get-go, S.H.I.E.L.D. had lifelike robots that could, in secret, replace human beings and fool friends and foes alike. What could possibly go wrong?

Let’s start with “Nick Fury vs. S.H.I.E.L.D.,” a 1988 story that bears the most resemblance to what’s happening on TV. Nazi scientist Arnim Zola created an LMD called the Deltite with the mind of Baron Wolfgang von Strucker. Zola had Nick’s estranged brother Jake Fury smuggle it on board a helicarrier for some future evil purpose. The LMD became self-aware, though, and — not realizing it was really Strucker — started replacing everyone in S.H.I.E.L.D., Hydra and A.I.M. with LMDs.

There’s also:

• That time in 1969 when a Tony Stark LMD became self-aware, then tried to kill Stark and replace him. (Not to be confused with that time in 2000 when one of Stark’s Iron Man suits became self-aware, then tried to kill Stark and replace him.)

• That time in 1977 when the Jake Fury LMD reprogrammed a Nick Fury LMD to think he was the real one, before he learned he wasn’t, and started calling himself Max Fury.

• That time in 2007 when She-Hulk had to fight a helicarrier full of Nick Fury LMDs dressed only in her (purple) bra and panties.

• That time in 2009 when a whole bunch of LMDs dressed like Deadpool tried to kill Deadpool. (Wait! That’s not a bad idea!)

• That time in 2014 when former World War II commando and S.H.I.E.L.D. deputy director Timothy Aloysius “Dum Dum” Dugan found out he was actually an LMD, with the original having died in 1966. (Sorry, Dum Dum!)

• That time in 1976 when Tony Stark created a Thor LMD, which he reused against his own friends in the comic book “Civil War” in 2006. (Does that guy never learn from his mistakes?)

It’s a shame that nobody took Agent Alphonso MacKenzie’s advice in “Agents of S.H.I.E.L.D” recently. He warned that you should never build robots, because they always rise up against you. Sorry, Mack!