Silly inconsistences ⇒

Saw two movies today, Back to the Future III and Interview with a Vampire. There were a few things that bothered me about these movies. In BttF III at the very end, Doc comes back with a time travelling train. Where did he get it from? Surely he couldn't have created it back in the 1800s?

In Vampire, if Louie was so upset at his life, why didn't he just kill himself? What was Lestat doing all those hundreds of years, just sitting in that chair? He couldn't do anything? And seeing Louie "woke" him up? I don't buy that. Also, why the helicopter? It came, shined its light in the window and then left. Don't make much sense.

Any explanations?