When Meg Oliver and her brother, Chris, were on their way to a Halloween party on October 30th, they find Bim stuck in a hedge. After he's pulled out, Meg and Chris continue on their path to the party. Later at home, Meg and Chris enter Meg's bedroom to find Bim in it. Bim tells them the package was an aroma message he sent to make them come home, because he felt lonely. He introduces himself to them and says that he came from Weirdo Planet. Meg and Chris didn't believe him and told to go home but he stated that he now belongs to them because they pulled him out of the hedge. Meg picks him up and tries throwing him out but he rapidly gained weight forcing her to put him down. This causes Meg to lose it and start tugging at Bim's chin. That when Chris and her realized that Bim really is a alien.
Chris asked Bim why he came to Earth, but he couldn't remembers lending on Earth messed his mind up. Meg and Chris once again told Bim to leave which made him angry, causing him to drool, his fangs to slid down over his chin, his chest to swell, his face darkened to purple and made him pant and snarl like a fierce animal. As his face brightened to tomato red, Bim told Meg and Chris that he shouldn't be angered.
On Halloween night, the kids tried to ditch him at a party but he got back home thanks to his Weirdo Tracking.. He got mad and became a monster again. Meg, Chris, and their friends Carlos and Kelly started throwing stuff at Bim, but when Meg threw a toy they got from Chiller House called a Floig, he returned to normal.
Bim had finally remembered that the Floig was the reason he came to Earth and that the trip made it forget. Now reunited with his favorite toy, Bim left. A few seconds later, six Weirdos identical to Bim came in Meg's room through a broken window saying they've got Bim's invitation to move in. But when Chris and Meg tell them Bim went home, they all returned to Weirdo Planet to try and catch up with Bim.
Bim is about three feet tall, has damp, hot, lumpy, sticky and shiny orange skin, a bald head with two snail-like antennae on top, a scrawny neck, a baby face with two tiny, black raisin-like eyes, a crooked smile, a round chin, three rows of straight yellow fangs, a fat pink tongue, little arms with three-fingered hands and a slender chest. He wears a blue T-shirt over a big diaper along with shiny red shoes.
Bim is very childlike, as he often gets angry when he doesn't get his way. He doesn't understand how Earth society works, as he believes that throwing a stink bomb (which he calls an aroma message) into someone's window is complimentary. Despite this, he is willingly to leave when he finds what he wants.