This episode reveals that Terry's age is seventeen. Later, in the Justice League Unlimited episode "Epilogue", Terry imagines quitting as Batman, and mentions how he was sixteen when Bruce started training him. This indicates that by this episode, Terry has been Batman for roughly a year.
Bruce Timm reveals that "Earth Mover" is one of his favorite episodes. One reason for this, he says, is that it is more ambiguous in its morality -- its "villain", Bill, is not a thoroughly evil man, and has tried to make up for his past misdeeds, while the main antagonist, Tony, has understandable motives for his acts, but is irredeemably destructive.