Alex first appears in the movie working on the house paint with his brother, Nathan, and their friend, Ozzie. While there, Alex and Ozzie wind up painting Ozzie's face due to their antics. When Ozzie goes inside the house to clean up, he runs back out to tell Alex, Nathan and Tory, the owner of the house, about being threatened by a Leprechaun, only to be met with skepticism by the others.
Later on, Alex and Ozzie spot a rainbow in the sky and follow the end to an abandoned truck, where they find a bag of gold. Ozzie, while trying to check if the gold is real, accidentally swallows a coin. Alex, meanwhile, tells Ozzie that they can use the gold for an operation to "fix" Ozzie's brain.
A little while later, Tory's father, J.D., is bitten on the hand, so Alex and Ozzie hide the gold in the well until they get back from the hospital.
After dropping of J.D., Tory and Nathan go to a diner while Alex and Ozzie go to coin-store owner Joe to determine the gold coin they found. Joe confirms that the gold is real and asks to keep it overnight to study it, to which Alex and Ozzie agree. After they reunite with Tory and Nathan, they take off back to the house. While, they are gone, Joe is killed by the Leprechaun.
After arriving back at the house, the four are then attacked by the Leprechaun. After various attempts to escape, they are then driven back into the house. Ozzie eventually tells them about the gold, so Tory goes to the well and gives the bag of gold to the Leprechaun, hoping it will now leave them alone. However, the coin that Ozzie swallowed prevents this.
After the Leprechaun attacks them again, Ozzie suggests that Tory goes to Dan O'Grady for advice on how to kill the Leprechaun. Alex, Nathan and Ozzie then distract the Leprechaun by throwing their shoes at him for him to shine, which he cannot resist. While they do this, Tory takes the car and drives to the retirement home where O'Grady resides. After she leaves, the trio go back into the house.
After Tory returns with the news that four-leaf clovers will help them with the Leprechaun, they search in the clover patch nearby, but the Leprechaun attacks them again, so they have to run away. After they search and run, they finally find the clover. The Leprechaun gets into the house and almost kills Tory, but Ozzie saves her by telling the Leprechaun about the coin he swallowed and running outside with the Leprechaun chasing after him.
When the Leprechaun pins down Ozzie and starts injuring him, Alex takes the clover and sticks it in a wad of chewing gum and puts it in a slingshot. After finding the Leprechaun, Alex curses at it and fires the clover into the Leprechaun's mouth, causing to stumble back and fall down the well. When it comes back, Nathan knocks it back down, fills the well with gasoline and sets it on fire, causing an explosion, finally defeating the Leprechaun.