It is white milk that looks just like ordinary milk from the real world, except that it is solid by the time Patrick has it, due to it spoiling. In its solid state, it closely resembles a marshmallow, bearing a similar squishy texture.
Role in episode
After Patrick wails at the mention of the Dirty Bubble challenge, SpongeBob invites him to have some kelp cookies and a glass of seahorse milk. Patrick judges how long Gary has been missing and SpongeBob took the Dirty Bubble challenge based on the condition of the milk, revealing the duration to be 10 days.
Role in Where's Gary?
It plays the same role in this book as it does in the episode.
- It is a parody of horse milk.