Dan talks about using a crayon to draw on walls; crayons weren't invented until1903.
At about 1:10 while Don Murray is putting his shirt back on for dinner, the outline of his watchband is clearly visible on his left arm.
Alan Ladd injured his hand while working at his ranch during the lay-off in the March-April 1960 Screen Actors Guild strike against Hollywood studios, but was well enough to resume filming.
A bit of what could be interpreted as sexual innuendo when Dan Keats, who is obviously in love with Julie, is shirtless and washing up to eat. Julie scolds him for splashing water on her clean floor. As they face each other and as Julie is patting Dan dry with a towel Dan asks Julie "did I get you wet?" This appears to be a sexual double entendre reference to her becoming sexually aroused.