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.
Question: After just a few series Tommy's girlfriend Stacey left the show. Does anyone know why?
Answer: She left with her new boyfriend to go to a English college.
Question: Can someone PLEASE explain the ending? The whole show was pretty confusing, particularly why everything disappeared at the end, why people lost their memories, etc.
Chosen answer: The show was originally planned to have a second season, but then it was dropped because of low ratings in Japan, thus the abrupt ending leaving everything unexplained and out in the open. Still, the show was so popular on TV in the US that The Cartoon Network decided to finance the production of the second season, which is right now coming out on DVD (I think the first three volumes are already out). This should end up tying everything nicely.
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.