‘Joker: Folie a Deux’ review: Lady Gaga and Joaquin Phoenix sing for no reason in pointless sequel

The DC dirge “Joker: Folie à Deux” is a sequel in search of a purpose.

For nearly two and a half hours, director Todd Phillips’ pathologically unnecessary movie cycles through so many potential reasons to exist.

But, as “Deux” grows increasingly disturbing, repulsive and strange on the hunt, it ultimately never finds a satisfying one.

First, the film exhaustingly tries dragging out the story of Arthur Fleck, the mentally ill aspiring stand-up who snapped and killed a late-night talk show host on live TV in the last one.

Joaquin Phoenix won an Oscar for playing the traumatized loser who is essentially Robert De Niro in “The King of Comedy,” plus clown makeup. So, let’s milk it for all it’s worth.

But the truth is that the whack-job Gothamite with no Batman to battle is more weird than he is involving.

Aimless, Arthur whispers, glares, yells, rails against the world and does his creepy laugh again and again with nothing to show for it. This time, we care neither for nor about him.

Since Arthur’s static journey behind bars alone is not meaty enough for a second chapter, another justification “Deux” flirts with is a creepy concert for Phoenix and Lady Gaga.

The pop-star-turned-actress plays Harleen “Lee” Quinzel — aka Harley Quinn — a troubled woman locked up in Arkham Prison enamored with Arthur and his rage-driven Joker persona.

He’s become a cult hero since his six-victim killing spree, and a made-for-TV movie about his crimes has gained him legions of messed-up fans like Lee.

Phillips, who clearly dreams of working for MGM during the 1940s, somehow saw this as a logical opportunity for the pair to perform a Broadway musical’s worth of songs — a good fifteen, all told.

The choice brings to mind a song from “Miss Saigon”: “Why, God, Why?”

When they nearly escape Arkham, Gaga belts out “If My Friends Could See Me Now” from “Sweet Charity.”

After Arthur learns he’ll stand trial for his crimes — his lawyer plans to argue split personality disorder — he croons Stevie Wonder’s “For Once In My Life.”

As he falls hard for Lee, the smitten inmate performs “Bewitched, Bothered and Bewildered” from “Pal Joey.”

Bothered and bewildered, I was.

Because the ballads, duets and production numbers featuring ballroom dancing and tap are frightfully awkward and don’t add anything meaningful or worthwhile.

The sequences are not campy, enlightening, emotionally powerful or dazzling. What are they? About three minutes each. I’d never listen to any of these covers.

Really, the rationale for “Folie à Deux” hitting theaters is simple. The first film, meant to be a one-off, unexpectedly grossed more than $1 billion at the worldwide box office. So, here’s a visually sumptuous cash-grab follow-up.

Besides the admittedly alluring aesthetic, with pops of color bursting through grotesque grime, Phoenix and Gaga are quite good and effortlessly click.

Both love playing psychos and are far better suited to a DC Comics asylum than the Palace of Versailles or the “House of Gucci.” They do deranged disconcertingly well.

Their material, though, is thinner than Joaquin after his sickening bodily transformation for the part.

Phillips’ plot, almost all of which is set in a prison and courthouse, amounts to a suspense-free legal drama and a trite serial-killer romance.

“What’s a nice guy like you doing in a place like this?” Lee’s eye-roll of a first line to Arthur goes.

“I killed five people — one live on national television,” he matter-of-factly responds, finally discovering the comedic timing that’s so eluded him.

The second half of “Deux,” featuring the talented Harry Lawtey from “Industry” as Harvey Dent, is all “order in the court!” “I object” and “Next witness!”

And, I regret to inform you, more pointless songs.

“The clown with his pants falling down / Or the dance that’s a dream of romance / Or the scene where the villain is mean — that’s entertainment!” a dejected Arthur sings.

Perhaps. But excessive, regressive “Joker: Folie à Deux” is not.