Elmo was created by master puppeteer Jim Henson in 1972 where he was just known as "Baby Monster". He wasn't that much exciting and was given the boot for the rest of the 1970s and early 80's. It wasn't until 1985 that Elmo came back to Sesame Street in his current appearence. He was now very dumb and kept annoying everybody on the show, including Kermit The Frog.
But 1990 was a tragic year, because Jim Henson died at age 53. Everybody was sad, except for Elmo. He thought "Now that he's dead, Elmo can take over the show!" And he did. He took over about a half hour of Sesame Street and called it Elmo's World. Not much else happened after that until 2002 when he became the president of PBS, which lead to the channels decline in quality a few years later.
In 2005, Elmo joned the newly formed group caled The Barney Bunch. However, he would often get badly hurt (and nearly killed) during most of the bunches rapings. He later quit so he would have more time to work on PBS. Members of the club would now call Elmo "The Benedict Arnold of The Barney Bunch". Elmo also quit the Evil Celebrities. Barney once said that "Elmo might be the most famous character on Sesame Street, but he's the most famous criminal. Elmo has caused more murders than me, and he has been taking drugs. Elmo soon met his fate at the hands of myself, when Elmo was murdered." After Elmo's murder, a clone of Elmo was made to serve out his roll on Seseme Street for the rest of the TV show's run.