Kate and Jack make chemistry

Eating crackers is a great way to feel better without becoming a fugitive of the law.

One can also tell that Jack Shephard is laughing by the way he shows his teeth while looking 90-degrees away from the person he's talking to.

Jack says Thanks

As a doctor, Jack Shephard knows that sandwiches are to be eaten and thanks are to be given, both at once.

i'm happy because you're happy

we also would have accepted "[chuckling]"

Car

i've never been very good at flashcards

Not Every nook and cranny, John

This is Sayid proving John wrong by mocking him through his own old-fashioned idioms. Similarly, the following exchange may have occurred on the island:

John: Sayid, I swear to you a bird in the hand is worth two in the bush.

Sayid: This bird in my hand is not worth the two in that bush, John. 

Any tea is Good tea