Question: How did the streetcar, phone booths, and vending machines end up in the digiworld?
Answer: People who built the digital world most likely had them sent there. Gennai tells the kids in the last episode that the streetcar was from San Francisco, and he asked them to take it back for him.
Biyomon Gets Firepower - S1-E4
Question: Why did Meramon act like he was in pain from his own flames by yelling "aah, I'm burning, too hot!" while sliding down Mihirashi mountain? Palmon says there's no reason he should be in pain from his own flames-that's his nature.
Answer: He was in pain from the black gear that was stuck inside of his body.
Question: Why are Digimon called digital monsters? They don't look digital.
Answer: Digimon started as a series of virtual pets, making them digital. In the television series, Digimon live in the "digital world."
Answer: We are never told as to how they got there.