Gary has white fur while Larry has gray fur; to differentiate them, they both have different eye colors. They both wear guard uniforms to indicate that they are asylum guards.
Both wolves take guard duties seriously. When they hear a howl, they can't help but join in, as they are both wolves.
Gary and Larry are seen as guards outside the Cliffside Asylum just as Judy Hopps and Nick Wilde are planning to find Mr. Otterton. In order to get inside without getting caught, Judy pretends to howl like a wolf, causing the two wolves outside to get distracted. Distracting the guards, Judy and Nick manage to get inside while Gary and Larry are still howling in order to find Mr. Otterton and solve the case. It is unknown what happened to them after Bellwether's arrest, even after the night howlers giving cure effects towards savage-infected predators in Zootopia.