Stranger in a Strange Land is better than you remember it to be.

I've seen this episode maligned numerous times; especially for Jack's flashback, but it actually serves more narrative purpose than it gets credit for. It was just poorly executed and a bit racist.

1. Jack: The tattoo stuff was silly; especially, cuz if you actually go to Thailand, (which I have) you can pay for tattoos and they will give it to you with very little issue, but money.
   1. The most important thing it does is set up "Through the Looking Glass". In this episode, you see the beginning of Jack's descent into alcoholism and emotional decline (also travel). So, when you see him in the beginning of the season finale, with a beard on a flight,>! you can easily assume that this is him in between his travels in Thailand and his father dying; rather than a flash forward. !< It's part of what makes the Kate reveal at the end so shocking.
   2. Jack's behavior in the episode, reveals more of his less-than-favorable qualities, especially his arrogance, which has consequences in season 5.
   3. It's also a major part of the arc that nearly got him off the island, until the sub got blown up in "The Man from Talahasee", collaborating with The Others and why the people at the camp didn't trust him when he came back.
2. The Others: It actually delivers quite a bit of exposition about the others then you remember. It gave insight into their hierarchy and culture, that had not been discussed before ( or after really); especially with the reappearance of Cindy and the children, but also that Ethan was a doctor.
   1. It develops Karl's character's relationship with Alex, which later pays off more when Ben talks about his extreme protective behavior and his estrangement from Alex. Karl also bonds with Sawyer, which sets up warning the camp about the Others coming in "Greatest Hits."
   2. It's a key part of Juliet's narrative, which also pays off when she leaves The Others, falling in love with Jack and then eventually Sawyer.
   3. The appearance of the Sheriff (even though it's her only appearance) does some work in peeling back the curtain on The Others, which is necessary for Locke's journey in season 4.
3. Sawyer and Kate: Continues to develop their relationship arc and the tension betweent them and Jack. It also has some irony, because the couples of Jack/Juliet and Kate/Sawyer switch.

If you take this epsiode out there's a lot that happens later, which doesn't quite make sense. The dialogue was poorly written, directed and acted, but narratively, it does a lot with very little.

Edit: Fixed a word mistake.