I love how developers sometimes slip fun, amusing or whimsical easter eggs into software. I was just taken by how the Ruby application server Puma's current version has a codename of "Llamas in Pajamas".
What are your favourite whimsical bonuses you've found in code? Have you slipped something fun into a project that left you giggling while you waited for someone else to find it? What are your favourite llamas in pajamas?