In "The Mark of Athena" by Rick Riordan, Leo is inspired to express himself by painting a massive greeting, "WASSUP?" accompanied by a smiley face on the bottom of a ship's hull. This idea reflects Leo's playful and carefree nature, embodying the humor he often brings to intense situations. However, Annabeth opposes the plan, suggesting that such a whimsical display might not be suitable for their serious mission.

The interaction highlights the dynamic between the characters, showcasing Leo's quirky personality and Annabeth's more pragmatic approach. Their differing views help to illustrate the balance between lightheartedness and responsibility that exists among the characters throughout their adventures.