Among the many varieties of items scattered about the house are 12 fl. oz. cans of soda. If you check the nutritional information on the side of one, you'll see that it claims to contain two 6 oz. servings.
Katie's thoughts of some items are revealed through the mouse-over captions. For example, when you find a book in your parents ensuite about helping older couples re-kindle their marriage, both personally and... physically?
At one point Katie finds a letter written by Sam, detailing her sex life with Lonnie. The letter remains open for about 5 seconds before it's closed automatically, with Katie's caption stating "Ok, not reading any more of that." You can try reading it again, but all that happens is a caption about how she's still not reading any more of that.
If there were such a thing as Fridge Funny, then that diary entry becomes it when you later find a note from Sam's parents about her grounding. One of the terms is Sam "cannot have the bedroom door closed when Lonnie is in the house." It's not hard to put two and two together.
Sam's Health Class assignment, which weaves an explanation of the menstrual cycle into a, erm... bloody story about a bombing raid in World War II. The teacher's comment at the end really sells it.
Just to let you know what a pompous ass Terry's father is, one of his published books is called Joyce: A Complete Understanding.