Grappling Hook / Wings of Rebellion
When the move is used, Joker will shoot a grappling hook upwards at an angle while being boosted up slightly (although the boost only works once in the air). It acts as a tether recovery, similar to the Ice Climbers' Belay and Ivysaur's Vine Whip, and can pull opponents closer to Joker if it hits them while Joker is grounded. It can also grab items. If used in the air, the move instead has a weak hitbox that can be used to push the opponent into the blast zone if they're already close. Also, Joker may utter one of the same voice clips used for his smash attacks, grunting or saying "There!" or "You're mine!" when using this move. Strangely, this move is treated as a projectile, and thus it can be reflected. However, instead of Joker taking return damage, the move is cancelled out, leaving both fighters unharmed.
Upon the throw's success, Joker gains enough frame advantage to always hit a forward aerial up until around 110%, giving the move a lot of utility. Grappling Hook's grab hitbox will not work if the opponent is already in hitstun, limiting its use to starting combos, not continuing them. It also does not work on shielding opponents, akin to Isabelle's Fishing Rod. It also has very few ways to confirm into it, with the last hit of up aerial while Joker is close to the ground being the only "true" one. A good way to set this up is during a fast fall up aerial. Outside of this, up tilt has situational use as a frame trap with this at lower percentages. Down tilt sends at a good angle for it, however the opponent can easily air dodge it if they react in time.
If Arsene is present when the move is inputted, Joker will instead use Wings of Rebellion (反逆の翼, Wings of Rebellion), which causes Arsene to allow Joker to fly upwards, or at a slight angle, akin to Power of Flight. Joker is intangible during Wings of Rebellion from frame 1 to 25 if used on the ground, and from frames 3 to 25 if it is used in the air. Much like Power of Flight, the move deals no damage and renders Joker helpless, meaning the Joker player will have to use it sparingly. It also has a much worse 2-frame animation, leaving Joker vulnerable to long-lasting hitboxes on the ledge, such as Banjo & Kazooie's down tilt. This can, however, be mitigated by using Wings of Rebellion closer to the ledge, where Joker's intangibility will make it much harder for him to be hit.
Joker can be seen using a grappling hook in some transition animations of Persona 5's pause menus, though he never uses one in the game itself until the re-release Persona 5 Royal.
In Persona 5 Royal, Joker uses a grappling hook to reach far-off locations when dungeon crawling. He can also use the grappling hook for combat; by increasing his rank in the Faith Confidant, he learns the Chaînés Hook ability, allowing him to latch onto unaware enemies from afar and zip towards them for an ambush (curiously, this is the exact opposite of how the attack interacts with opponents in Smash Bros.). The animation for the attack in Smash Bros., with Joker's spinning flourish before shooting the hook out of his left sleeve, is identical to his animation when using the grappling hook in Royal. Royal received its first previews showcasing the use of the grappling hook a few days after Joker's DLC release, heavily suggesting that the idea for having the grappling hook in his moveset came from Royal.
Wings of Rebellion has no solid base in Persona 5, but is likely based on the fact that Arsene is capable of flight. It is also a possible reference to the intro of the game, which shows Joker summoning Arsene to take flight. The name of the attack calls back to a speech that is heard whenever Joker begins a new Confidant: a voice informs him that the bond he has just forged "shall become the wings of rebellion that breaketh thy chains of captivity."