Irwin is a pudgy, nerdy, African-American boy and a close friend of Billy's. He says the word "yo" regularly. Unlike Mandy and Billy, who show no signs of fear for the frightening, supernatural and magical beings and settings around them when using Grim's magic to venture into the underworld (Mandy because of her fearless and sinister personality and Billy because of his ignorance), Irwin has displayed more signs of cowardice in such situations and seems to be more easily terrified than his friends when he accompanies them on such trips (such as in Big Boogey Adventure and Keeper of the Reaper). In one episode, it was revealed that Irwin's mother is a mummy (as is his maternal grandfather) and that his paternal grandfather is the bloodthirsty Dracula, who is married to Irwin's saucy paternal grandmother Tanya. Because of being related to such peculiar monsters, Irwin has been shown to possess superpowers which he displayed basically just in a single episode. In "Underfist", when using his newly discovered powers Bun-Bun and Mindy remark in a very impressed way that Irwin's supernatural abilities and dark powers are truly amazing. Irwin is famous for his deep romantic infatuation with Mandy, in spite of her extraordinary hatred of him. In one episode it shows that he would even make her love him by the use of Grim's mystical scythe. His deepest fear is shown in Big Boogey Adventure; telling jokes to wild bears. In very rare instances Irwin is shown to have an evil, darker and side to his personality. In the episode called Halls of Time, it is mentioned by Irwin that he has an older brother who picks on him so much that when they get a hold of his older brother's hourglass, Irwin destroys it while laughing in an evil manner. In another episode after Irwin's mummy grandpa shows up to commission a pyramid for his grandson Irwin first agrees to it because of impressing Mandy, but later gives in to it after developing a very strong lust for power. He then shows his more sinister side when enslaving all of the people of Endsville and zombifying them. This very rare darker side of his personality was finally explained in the series last episode called Heartburn. In it, Mandy discovers everyone's true heart through the use of Grim's special camera, but is greatly shocked when she discovers that one side of Irwin's heart looks like hers in a very creepy way. Irwin explains that when he was a baby he was born bad and evil, but had a change of heart when his human father showed him the meaning of respect, friendship, and love.