Yep, that's Northern Irish actor Declan Mulholland playing "Jabba the Hutt" in a deleted scene from A New Hope. This was never supposed to end up in the finished film, though: The plan was for Lucas to lay a stop-motion creature over Mulholland's performance ... keeping the thick Irish accent and all. This, of course, doesn't explain why the guy is dressed in that ridiculous costume -- maybe it was there to help Harrison Ford visualize the character, or maybe it's just what the actor came in wearing that day.
Star Wars Wikia
We assume all Irish people dress like this all the time.
So what would the finished version of Jabba have looked like? Something like this:
Your eyes do not deceive you. That's a slug violating an Irishman.
According to Lucas, he originally saw Jabba as "a big furry character," as opposed to the lovable slug we all know. That's right: Jabba the Hutt was dangerously close to being some sort of mean, morbidly obese Ewok. What Lucas has never explained, as far as we know, is why he chose to make him sound like an Irish gangster. We could be witnessing the first steps on the road to Jar Jar Binks here.
As fans well know, Lucas eventually included the deleted scene in the special editions, awkwardly inserting a CGI version of the Return of the Jedi Jabba and redubbing the dialogue. We kind of wish he had gone the other direction and instead CGI'd the fat, furry Irish guy into Jedi. Seriously, imagine Slave Leia strangling him.
Our statisticians estimate that four of you are now masturbating.