All I can say is wow! This episode had everything the last episode was missing. It focused on just the key characters with no pointless digressions, it was tightly written with many "in" jokes used and it drove the character development and overall season arc forward.
I must say that while I hold Sam Witwer near and dear to my heart as one of the hottest up-and-coming actors in the genre, (Smallville, BSG, The Force Unleashed), I have to say I am glad he did not make an appearance in this episode. We needed a break from the Doomsday-drama. Also, it would have detracted from the main plot of the story, much in the way Tess's story line did in "Turbulence". I have always found that while ensemble casts can make for an excellent series, they have to be kept within a reasonable number of players, otherwise there just isn't enough air time to do each character justice. (This is, of course, the very problem that is currently plaguing Heroes.)
In "Hex", another DC character, Zatanna Zatara, is introduced. Zatanna is a magician with actual magical powers and she goes through the cast of smallville granting wishes to all and sundry. Due to Clark's continuing desire to be normal, we find ourselves for the second time in a position where Clark has forgotten who he is and Chloe has to help him remember. This created some very amusing moments as always, but I found this portion of the episode to be the only bit I found stale. It has been done to death. Of course, the situation of Clark's memory loss is made even more difficult when Chloe is turned into Lois! It is understandable that Chloe would be jealous of Lois, as Lois is living the life Chloe always thought she wanted, but when you add a magician and a birthday wish to the mix, apparently Allison Mack gets a couple of days off.
I particularly liked that living a day in Lois' shoes makes Chloe realize that she is no longer the intrepid reporter. Her character used to be defined by her curiosity and her reporter insticts all the way back to the Torch and the Wall of Weird. Since learning Clark's secret, she has been so much less the reporter and more the supporter, and it is nice to finally have it acknowledged. The epiphany she has at the end of the episode makes for a very satisfying conclusion as she joins the slowly coalescing JLA, (though it hasn't "officially" been named yet).
One thing I have always loved about Smallville is the way they can write in a character from the DC world that may not be widely known and still do justice to the character. At the same time that they are writing in the references of comic lore for the fans, they are also presenting the character in a way that will allow non-comic readers to quickly become acquainted with him/her without a great deal of boring exposition. They did it in the past with A.C., Impulse, Black Canary and many others who have since made multiple appearances.
While I don't think that Zatanna will be making a return visit any time soon, I do feel that the character was treated properly. The character was well cast, and the costume was perfect. The plotline for her character, trying to recover her father's book of magic to bring him back from the dead, is a call back to her first appearances in the DC universe. I don't doubt that she will return to Smallville again at some point.
After all, nothing solves a confusing plot conundrum like a little bit of magic.