A wanted poster from the Joker can be seen on a wall in the old police headquarters building. The photo on the poster had to be taken during The New Batman Adventures (1997) since the Joker features the same character design as in that show.
It is explained why Bruce never refers to Terry as "Batman" during his investigations. However, Bruce later does once in the episode "Ascension", mainly because he is publicly saved by Terry from Blight.
The car that Terry is driving resembles the Batmobile from Batman: The Animated Series.
When Shriek is revealed to have gone deaf, there was a high-pitched ringing tone in scenes shot from his point of view, implying that he had actually acquired tinnitus as a result of the malfunction of his suit.
Shriek's suit may be modeled on old Kryptonian technology seen in Superman: The Animated Series, Season 2, Episode 1 titled "Blasts from the Past: Part 1" Beginning round the 6:20 minute mark you can see a swarm of soldiers in white uniforms and helmets designed with distinct circular modules styled like the one worn by Shriek; their helmets, gloves, and chest plates have these circular modules. Around the seven minute mark, Jor-El, Superman's biological father, is seen manipulating one of these Kryptonian helmets causing it to "shriek"; the emitted sound causes the soldiers to cover their ears.