Joffrey seized the Iron Throne in the HBO drama's first season and later ordered the death of Ned Stark (Sean Bean).
Gleeson told Entertainment Weekly: "With his coronation, his malicious deeds amplify tenfold," "There are scenes where I just do malicious things for no reason.
"He thinks everyone should say yes to him, because he has the right to be where he is, so he doesn't take no for an answer."
The Irish actor also revealed that Joffrey will continue to rebel against his mother Cersei (Lena Headey).
"I'm changing up the design of the Throne Room and kind of throw my toys all over the floor," he said.
Gleeson added that the reaction to his character from Game of Thrones fans has been "nothing but lovely".
"I haven't gotten anybody coming up to slap or yell at me," he said.
Game of Thrones will return on April 1 on HBO in the US and on April 2 on Sky Atlantic in the UK.
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Watch a Game of Thrones featurette on Joffrey Baratheon below: