If you've got the time this video is really worth a watch, but since this is a long one, here are the highlights:
The actor, Ahmed Best, was originally hired just to do the on screen physical acting for Jar Jar, but he sent in a voice audition with 5 or 6 different potential voices, and George Lucas fell for that weird Jamaican-esque accent we all know and cringe about. Best says it's his "generic little kid voice," which Lucas loved because Jar Jar was supposed to be very immature.
Best describes the Jar Jar backlash as being a painful experience, and makes it really hard not to feel bad about all the shade you've been throwing at Jar Jar for nearly two decades:
One of the biggest reasons I took it was because of the challenge of it—there was no Andy Serkis and Gollum, Navi fromAvatar, Martians, John Carter.
I was to be the template for this, so I was kinda working with George to pioneer this new character form of acting and storytelling. On set we were all just so focused on the challenge of it and having so much fun that the post-Star Wars stuff was a surprise. Even though you play characters, you put a lot of your own personality into it, you get emotionally and personally invested in the work that you do, it’s your work and you take pride in it. So when your work is criticized negatively, you feel a hit.
Best also confirmed that Michael Jackson was interested in the role of Jar Jar, but ultimately Jackson didn't play him because he didn't believe Binks should be CGI.
Last but not least, Best says he would turn down the opportunity to bring Jar Jar back, so you can hang up your Supreme Leader Binks hat.
If nothing else, you should head to 8:50 in the video, where Jar Jar does lines from Taken.