So, Doc Brown didn't leave Marty in 1955 on purpose. The lightning that struck the flying DeLorean accidentally triggered it to time travel back to 1885 (remember that the DeLorean's date function was malfunctioning throughout the movie; you should be able to see the exact point the date changed 1985 to 1885 the next time you watch it). So, obviously the movie got A LOT wrong about what 2015 would be like (it would be great if pizzas were that easy to prepare!), but it's still fun to see the creativity of what they came up with (still waiting on the flying cars)! This crazy ride concludes with the 3rd and last movie. Can't wait to see your reaction to it!