At one point Booster Gold talks with a Superman/Batman hybrid with Wonder Woman's voice, this form resembles Composite Superman.
This story was originally going to focus on superhero Firestorm, but he died in the comics before the start of the season, and his successor, Jason Rusch, was not introduced in his place yet so couldn't be used, so it was changed to focus instead on Booster Gold.
Lori Loughlin played Carolyn Lance, a former Black Canary, and the mother of one of the main heroes, on the short-lived Birds of Prey (2002) TV series.
Plastic Man is mentioned here but is never seen in the DCAU. Whether his non-depiction is simply an oversight or due to legal issues is not clear. All Dwayne McDuffie knew was that the show's staff wasn't doing him. He is merely a dropped name and a rare "name only" cameo by a DC Comics superhero.
In Keith Giffen's Formerly Known as Justice League comedy 6-issue mini-series, Booster Gold and Elongated Man, as well as Fire And Captain Atom, who make cameos here early on, are members of the Superbuddies.