A couple of questions I have about screen writing

Does a pilot episode need to relay the motivations behind the protagonist's actions or can that be built up for the next immediate episode? Is the apparent dedication the protagonist has for the actions he/she takes enough to sustain an audiences' interest in the plot's development?

The most concideraly joyous films ever made

Wristcutters: A Love Story
Wall-E
The Great Dictator
Totoro