The Legion say that they have records of Lois Lane, Lana Lang, and Jimmy Olsen, but they have no record of Chloe Sullivan. Lois, Lana and Jimmy were all actual characters in the Superman comic book, but Chloe was invented for the show.
When the Legion mentions Brainiac 5, it is not only a reference to the comic book character, but it would also be Brainiac's 5th incarnation on the show: #1 Milton Fine who Clark defeated in the Fortress of Solitude, #2 stabbed with the Kryptonian dagger in Vessel, #3 electrocuted in the Arctic, #4 Brainiac possessing Chloe here, and finally Brainiac 5.
At the Daily Planet when Chloe downloads to the servers, the screen shows three green orbs with bolts between them. This is the iconic symbol of Brainiac since his inception in the early comics, most notably on his forehead.
Garth says "No glasses, no tights, no flights. So far, he's nothing like the Man of Steel." This is a reference to the show's rule of not having Clark fly or wear his trademark blue tights and the fact that Clark has yet to wear glasses on a regular basis.
This has one of the longest "Previously on Smallville" sections, at 1 minute and 23 seconds.