Boo Fly first appeared in "Match Maker" as one of the many monsters Ludo brings with him to Earth to fight Star and Marco. But is soon defeated and retreats back to Ludo's dimension.
He then appears in "Britney's Party" where he and the rest of Ludo's army hijack the party bus and redirect it to a dimensional portal. Star fights them on the roof and defeats them. They are last seen leaving the bus in pain and agony.
He is in the beginning of "Lobster Claws" with Ludo and the rest of his army fighting Star and Marco. He is then blasted with fiery cupcakes and is defeated due to Lobster Claws' incompetence. He then leaves Earth and later returns to get the wand again. When Lobster Claws gets it he and the other monsters watch in amazement. Then gets blasted with a daisy explosion.
He appears in the beginning of "Fortune Cookies" once again fighting Star and Marco, but is easily defeated. He then appears in the castle breakroom stuck in a water jug. Then secretly putting a kick me sign on the back of Frill-neck Monster. When Toffee sets up a trap Boo fly swaps Star's fortune cookie and soon attacks her and Marco. But gets defeated with a mushroom blast.
He appears in "Marco grows a Beard" with the other monsters trying to get the wand. When they failed Ludo immediately blames them for losing to get the wand and takes away their milkshake privileges. But Toffee convinces them to turn on Ludo which they did.
He appears in the season 1 final "Storm the Castle" where he appears in Star's room wearing Marco's jacket informing her where he is. He offers Toffee a stack a pillows but he rejects them and instead goes to make him a sandwhich. After Star destroys the wand with the whispering spell, Boo Fly somehow survives.
In "On the Job", Boo Fly works with Buff Frog and other monsters to get some food.
He then appears in "Is Mystery" playing with Buff Frog's tadpoles.
He briefly appears in "Mathmagic" where he is seen in Star's classroom in her vision.
Toffee | Ludo | Meteora Butterfly | Mina Loveberry | Tom Lucitor | Gemini | Rasticore | Seth | Giant Spider | Bald Eagle | Buff Frog | Bearicorn | Beard Deer | Three-eyed Potato Baby | Big Chicken | Two-Headed Monster | Giraffe Monster | Boo Fly | Lobster Claws | Warthog Monster | Crocodile Monster | Frill-neck Monster | Lizard Monster