The Tarantula was seen in the first film, "Home Alone" and Buzz McCallister keeps one in his room, in a fish tank on a loose-shelving unit. When Kevin was left home alone and attempted to climb the shelves to get to Buzz's life savings, his weight broke them and came tumbling down. While Kevin dusts himself down and grabs the savings, the tank has also shattered, causing the tarantula to escape, as it is seen wandering the house for the rest of the film.
In another scene as Kevin was cleaning himself in the bathroom, the tarantula can briefly be seen crawling next to the toilet. As Kevin prepares the traps in preparation for the night ahead, the spider can be seen wandering the house in various locations (on a wooden shelf, running across the front room etc.) During the trap scene, Marv tripped on a rope and grabbed Kevin by the leg as he tried to escape to the third floor. Kevin saw the tarantula crawling along the steps and tries to reach for it. The spider does not bite when he reaches for it and Kevin, able to pick up the tarantula, places it on Marv's face, causing Marv to comedically shriek like a little girl and giving Kevin a chance to reach the attic. Frightened, Marv, still shrieking, throws the spider on Harry (who was knocked out), grabs his crowbar and Harry, who had awakened, asked Marv what he was doing. Marv told Harry not to move, and while the tarantula was still on him, Marv hits Harry in the belly with the crowbar, only missing the spider by inches.
Whilst Harry argues with Marv for hitting him with the crowbar, the tarantula flees the scene and is not seen for the rest of the movie, but is presumably found by Buzz when the family returns home when he discovered the mess in his room.
Trivia: The species of tarantula featured in the film has for years been presumed to be the Chilean Rose Tarantula (also known as Grammostola Rosea) since this species is a frequently used spider in movies because of its compliant nature and wide availability. However, the actual species used is now reportedly to be the Costa Rican Zebra Tarantula (Aphonopelma Seemani), as hinted by its orange web spinnerets and striped legs clearly visible on its legs throughout the film, a distinctive feature of this species.