The other day I met a Lost Uber-Geek who told me some interesting things he's noticed about the show:

- Jack's dad goes to Australia to meet his daughter. The woman who tells him to fuck off is Claire's mother. Therefore, Jack is Claire's brother.
- The real "Sawyer", the man who conned Sawyer's mom and indirectly caused her to kill her husband and herself (right? or something like that) is the guy who also played Kate's dad.
- The first thing we see in the first episode is Jack's face as we wakes up in the beach, right after the crash. If you pause the image, you can see the weird black bee-like stuff reflected in his eyes.
- The tail of the airplane has the Dharma Initiative logo.
- When we see Jin and Sun standing in the airport and she accidentally spills something on his shirt, when they leave you can see someone who looks exactly like Jin standing in the background.
- One of the guys in the antactic station at the end of season 2 looks exactly like Jack, if you look carefully.

The guy thinks these last three "facts" mean that everyone in the island is a clone. I kinda buy the first two (I'd heard the first somewhere else), but I'm not sure about the others. Unfortunately, I can't be arsed to check the episodes for any of these things.