The Joker is one of the most popular fictional characters ever; Batman’s deadly archenemy managed not only to make some of the hero’s (and overall DC’s) greatest comics, but also to appear in multiple Batman movies, and for each of his appearances we have a great and iconic performance. After Suicide Squad, Joker (portrayed by Jared Leto) got a lot of attention once again - although his on-screen time was quite small - to the point where Warner Brothers recognized his popularity and his potential and decided to give him his own place in the DCEU.
He isn't an easy character to portray, both due to his looks and to his twisted and particular personality which takes a lot of effort and talent to portray well. He was created by Bill Finger, Bob Kane & Jerry Robinson; he's been around for 77 years. His first appearance in comics was in Batman #1 (1940): his clown look, maniacal laugh, creepy smile and dark humour attired people since the start and gave him that something unusual and particular that made comic readers like him so much; everyone wanted more of him, and from that moment on, he kept making more and more great stories until becoming Batman's most relevant and iconic villain.
He has one of the biggest number of victims (2000, children & women included; as stated in Devil’s Advocate); that’s probably because he always goes for mass homicides, often using his laughing gas (Joker venom) to kill as many as possible (through water conducts, for example).
Another known “ability” is how he manages to survive every time his plans fail: a helicopter’s crush, falling off a roof, even getting shot won't kill him (many people state that this “superpower” is simply his real-world popularity, which might be true, but Joker has always managed to survive the craziest situations since the start). It's also a common thought that Batman could simply kill him, but that's what Joker wants, so he would win either way, and in the this case he'd probably take Batman’s solid morals and sanity away - plus, if writers always fully used the superheroes’ potential, we wouldn't have half of the great iconic villains we have today.
And anyways, who says Joker would be so easy to kill?
He has genius intellect, and his way of thinking is so unique that there are many theories going on about his mind: the super-sanity one is an example, or the one in which he’s seen simply as an evil man that pretends to be insane to avoid the death penalty. He's not known for his fighting skills because they always depend on who's writing him, but he does have a very high pain tolerance.
He's also a very mysterious character; his origin is unsure although in The Killing Joke we’re told that before he became the notorious criminal he was a comedian named (or at least he was trying to be) Jack Napier, and before falling in a vat of chemicals that gave him the clown look, he lost his seven-months-pregnant wife.
And so, after reaching a certain level of popularity, he was given space in Batman (1960), a tv series where he was portrayed by Cesar Romero, who gave us a great and funny representation of the character. Nowadays Cesar’s performance is underrated, at least that’s what it looks like to me; perhaps that's because he was a very comical version of the character compared to the next ones: indeed, the most recent Jokers are darker than the 60’s version. That's perfectly normal, because comics have changed since those years, by taking a more serious note; today’s comics have more psychologically deep characters who face more realistic problems (this is very relative, since a story with an alien like Superman is not realistic at all; but the obstacles can be interpreted socially, morally, etc). Not that old comics never had those details, they did, but in this era they're amplified.
And so after Cesar Joker is brought back in Tim Burton’s Batman (1989), where he is portrayed by - the great - Jack Nicholson (one of my favorite Jokers). This version is already darker than Cesar’s version. He has a great maniacal laugh, he's quite creepy even before becoming the Joker, and the evil smile is of the best, creepiest details. This version is not only supported by Nicholson’s talent and creepy makeup, but also by a good script and a good plot, in which Joker tries to kill all of Gotham’s citizens by using his own toxins, something that happens quite often in comics (like in The Man Who Laughs, for example).
And then in 2007 we have the most popular and loved version of the Joker in The Dark Knight by Christopher Nolan, where the Joker is portrayed by the amazing Heath Ledger, whose Joker was an alternative version with scars at the corners of his mouth, that fans didn't mind at all. This one was the darkest and more dangerous version of the character, so many of his lines are unforgettable. And although some absurd and fake rumors going on about the actor such as “Heath slept two hours night to go crazy for the role” (a total lie - he was going through family and drug problems), in order to make it look like he actually lost his mind at some point, Ledger's performance was great because he had real talent and a good script.
After Ledger, the next Joker is portrayed by Jared Leto, as I said before, in Suicide Squad by David Ayer. This version has brought to some debates about whether that Joker is a good version or the worst one in history. Jared is a good actor, but the script was poorly written, and his look wasn't one of the bests (you probably heard about the "Damaged" tattoo on his forehead).
Now there are rumors going around about a Joker origin movie situated in the past showcasing a young Joker (meaning that a new, younger actor will be cast for the role). It does make fans excited, but also worried since the last version of the Joker wasn't their "cup of tea”. Everyone hopes for a better version, I personally would like to see a much more comics-accurate one, and I'm not only talking about his look, but about his personality as well. If there's one thing that's sure is that Joker will always attire people and that's why an origin movie about him might be a good thing for DCEU: everyone will have a deeper look at the character, some of his mysteries will be revealed, and besides that, having the Joker and Batman together on the big screen again surely wouldn't pass unnoticed. Indeed, instead of giving confirmations of his next appearance in Suicide Squad 2 and giving him 10 minutes of runtime, it would be better to give him a bigger role in a Batman movie, where his potential can be fully used.
No matter which actor portrays him, he always gets most of the attention when he's on the big screen!