Chloe's code name, "Watchtower," is the name of the JLA headquarters. Additionally, Chloe's basing in a clock tower and role as a computer-using coordinator for the team greatly resembles the comic book character Oracle.
First time Arthur Curry is called Aquaman.
This is the 11th episode of the season and the start of an annual unofficial tradition where the 11th episode of each season introduces a new character(s), a new hero team or has returning superhero guests. Justice introduces Smallville's version of the Justice League and has a super guest cast consisting of Impulse, Aquaman, Cyborg, and Green Arrow.
In the episode the various heroes are given code names. "Watchtower" for Chloe as the team coordinator and intelligence asset in homage to the role usually played by The Martian Manhunter for The Justice League in the comics. "Boyscout" for Clark is in homage to a common nickname Justice Leaguers have for Superman, "The Big Blue Boyscout". In the comics Batman gave "Impulse" his code name. Batman meant it sarcastically, hence the joke about how Bart didn't get to choose his own code name.
After being rescued by a super-speeding Impulse, Chloe remarks to Clark, "I thought you were the fastest man alive," traditionally used to describe the Flash.