Answer by taking a quote from the following article:

The Joker is a fictional supervillain created by Bill Finger, Bob Kane, and Jerry Robinson who first appeared in the debut issue of the comic book Batman (April 25, 1940), published by DC Comics. Credit for the Joker's creation is disputed; Kane and Robinson claimed responsibility for the Joker's design, while acknowledging Finger's writing contribution. Although the Joker was planned to be killed off during his initial appearance, he was spared by editorial intervention, allowing the character to endure as the archenemy of the superhero Batman. In his comic book appearances, the Joker is portrayed as a criminal mastermind.

The Joker was one of the few popular villains continuing to appear regularly in Batman comics from the Golden Age into the Silver Age, as the series continued during the rise in popularity of mystery and romance comics. In 1951, Finger wrote an origin story for the Joker in Detective Comics #168, which introduced the characteristic of him formerly being the criminal Red Hood, and his disfigurement the result of a fall into a chemical vat. By 1954, the Comics Code Authority had been established in response to increasing public disapproval of comic book content. The backlash was inspired by Frederic Wertham, who hypothesized that mass media (especially comic books) was responsible for the rise in juvenile delinquency, violence and homosexuality, particularly in young males. Parents forbade their children from reading comic books, and there were several mass burnings. The Comics Code banned gore, innuendo and excessive violence, stripping Batman of his menace and transforming the Joker into a goofy, thieving trickster without his original homicidal tendencies. The character appeared less frequently after 1964, when Julius Schwartz (who disliked the Joker) became editor of the Batman comics. The character risked becoming an obscure figure of the preceding era until this goofy prankster version of the character was adapted into the 1966 television series Batman, in which he was played by Cesar Romero. The show's popularity compelled Schwartz to keep the comics in a similar vein. As the show's popularity waned, however, so did that of the Batman comics. After the TV series ended in 1968, the increase in public visibility had not stopped the comic's sales decline; editorial director Carmine Infantino resolved to turn things around, moving stories away from schoolboy-friendly adventures. The Silver Age introduced several of the Joker's defining character traits: lethal joy buzzers, acid-squirting flowers, trick guns, and goofy, elaborate crimes.

What were some of the Joker's character traits?
lethal joy buzzers, acid-squirting flowers, trick guns, and goofy, elaborate crimes.