Re: How did TMP get a G rating?
Of course the movie ratings system in the United States is subjective (no idea how it works overseas). There's no formula for how a rating is determined, just a board of MPAA raters who decide based on...well, however they feel (with an unhealthy dose of influence from the major studios based on whatever marketing decisions they have made).
Kirby Dick's documentary This Film Is Not Yet Rated is probably the best source of information about the contemporary ratings system, although it is a few years old now (2006).
I found this which goes through some of the differences between the BBFC (Uk) and MPAA (U) rating bodies.
On the continent of wild endeavour in the mountains of solace and solitude there stood the citadel of the time lords, the oldest and most mighty race in the universe looking down on the galaxies below sworn never to interfere only to watch.