The Gurglings spawn as a pair and wander around the room. Each individual Gurgling has one attack in total which is performed independently of the other:
Rushes towards the player when aligned in any cardinal direction, leaving behind damaging Red Creep until they have run into a wall.
After rushing into a wall, they pause for a brief moment, and then spawn 0-2 Attack Flies.
Their dash can be interrupted if they run into an Attack Fly.
Champion Versions
Black: Gurglings spawn Troll Bombs at regular intervals instead of Red Creep when rushing towards the player. They take only 5 damage from their own bombs. They don't spawn any Attack Flies.
While petrified, the Gurglings take full damage from their own bombs.
Yellow: Three Gurglings will appear instead of two. They are faster but do not leave any Creep. They don't spawn any Attack Flies.
Gurglings appear to be the first stage of the "Gurdy" boss line, with the second stage as Gurdy Jr., the third as Gurdy, and the final as Mama Gurdy.
The Gurglings and their poop-themed variant, the Turdlings, spawn in groups of three during the Boss Rush.
If the Gurglings' audio is slowed down, the audio reveals that it is a little kid saying "Rawr!"
Unlike the regular Gurgling, boss Gurglings have a one-second death animation.
In the game files, the Gurglings' feet are called hands.
Bugs
Bug!
If the player stays close to walls, the Gurglings will not charge.
Bug!
If both Gurglings charge at once, only one of the Gurgling's grunting noise file will play.
Bug!
When fought in the Boss Challenge Room, they will appear in their enemy form rather than their boss form, making them much weaker and lacking a health bar.
Bug!
When the Gurglings are slowed and attempt to charge Isaac, they can't move and constantly spawn Attack Flies. Similarly, the "mini-boss" Gurglings attempting the same attack will constantly shoot 6 blood tears.