While fictional bands are not a concept created by this music duo, it certainly popularized it for modern audiences all over the world. At first there was The Archies (band comprised of the popular group of friends from Archie Comics) with their hit song 'Sugar Sugar' in 1969 which opened the door for the concept of fictional characters having a place in the music industry as their own stand alone visualized concept.
Gorillaz used the concept of a fictional band in a different way than The Archies. Instead of being a way to promote a show or comic series for commercial profit, the band was made as satire of the music industry. Lead singer of Brit Pop band Blur, Damon Albarn, was responsible for a lot of the creation of Gorillaz, basing characters and lore off of things he saw behind the scenes and mocked the fakeness of many musicians he saw on MTV. He worked with comic book artist Jamie Hewlett to come up with their fictional satirical band together. They united together to make the name as well, Hewlett stating in an interview that
We were born in 1968, under the sign of the monkey. Hence, the name of the band. I had proposed Chimpanzees, but Damon said no, Gorillas. I asked him why and he told me: "because they are bigger". Then we added a z. Because it is hiphop!
Listen to their music at the official Gorillaz Youtube channel
For further questions, go to: gorillazband@gmail.com