The Joker lazed in his cell in Arkham Asylum, throwing a deck of playing cards back and forth. Technically, he wasn't supposed to have the cards, but with a properly applied mixture of threats and ill-gotten cash, anything was possible.

"Joker's log, clown-date zero-five-eight point six," he said. "I am still in this pesthole where the natives try to get me to talk about my feelings." He sighed. "As I said on arrival, there does not appear to be a sign of intelligent life anywhere."

"Take that back, you clown-faced freak!" yelled the inmate in the next cell. "When I get out of here, I'm going to get you! An iron horse with a long tail—"

"Quiet down in there, Nygma!" a guard ordered. "The Joker was minding his own business, got it?"

The Riddler slumped against the wall of his cell and muttered anagrammed curse words to himself while the Joker laughed.

"Right," the Joker said after a while. He stood up and popped his spine and neck. "I think I've spent enough time here. Captain Clown is out!"

"Yeah?" the guard asked, walking over to the door of the Joker's cell and looking in, fingering the safety of his gun. "Listen up, you ain't goin' nowhere!"

"Three," the Joker counted down, "two, one."

A wall blew up, revealing the Joker's girlfriend, Harley Quinn, and a few henchmen dressed like clowns. "Set phasers ta 'kill'!" Harley said, swinging her giant, wooden hammer into the guard's head. He went down like a ton of bricks, and Harley grinned and saluted to the Joker while one of the henchmen got the guard's keys and unlocked the cell door. "First officer Quinn reportin' fer duty, Captain J!" she said.

"Took you long enough, ya dumb blonde!" said the Joker, stepping out of the cell.

"Well, we got here right when you were countin down," she said. "Besides, I had to round up the guys, get costumes on 'em, and we had to stop at the dry cleaner's!"

The Joker gasped in delight. "You mean—?"

"Yep!" confirmed Harley, producing a large plastic bag from goodness knows where. "We brought your suit, Puddin'!"

"Harls, baby, I could kiss you!" the Joker said. Harley closed her eyes and puckered up in anticipation, but instead felt the dry-cleaning bag get pulled from her hand and heard the alarms starting to go off. She opened her eyes to the sight of the Joker pulling his suit on over his Arkham inmate uniform, bathed in red alert lighting. He affixed his infamous flower to his lapel and relieved the unconscious guard of his gun. Glancing around, the Joker took note of the henchmen dressed as clowns. "Insane Clown Posse, eat your heart out!" he cackled madly, cocking his gun. "Babes," he put a hand around Harley's waist and pulled her close, "let's knock 'em dead."

…

Notes:

The Riddler's nonsense is the start of a riddle about needles. He was about to try and threaten the Joker. Bad idea.