Question: How did the streetcar, phone booths, and vending machines end up in the digiworld?
Answer: We are never told as to how they got there.
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.
Christopher - S4-E3
Question: How could Bobby be talking to Karen when she had just died in the car accident? he was stuck in traffic talking to her on the phone, and the traffic was caused by her accident, so she would already be dead.
Answer: Bobby Jr. was talking to his son (Bobby III) on the phone, not Karen. Karen couldn't get a hold of Bobby Jr, so she called her son and told him to give his dad a message. For whatever reason, Bobby III waited to call his dad (perhaps he couldn't get a hold of him at first as well). During this time, Karen had her accident and traffic backed up enough for Bobby Jr. to be stuck in it.
Thank you.
Question: What is the name of the theme song of Roswell? I think it's something called "Here I am", or "I am what I am".
Answer: It's called "Here With Me", performed by Dido. It can be found on her album "No Angel".
Answer: Everybody including Angel saw her. After helping them and then being left alone to talk to Angel, Cordelia says that the Powers That Be let her come back one more time to help them. After Angel gets a call saying that she died, he realises that it was her spirit that was helping them the entire time.