Yes, yes, yes! You spotted it! You have found The Pink Dolphin Easter Egg!
Pink Dolphins are a homage to Douglas Addams and The Hitchhiker's Guide to the Galaxy. You will find flying Pink Dolphins in several of the story of The Twighlight Manor series. They have no purpose, show up at random, and fly off into the night as quickly as they came.
The Twighlight Manor's Pink Dolphins made their first appearance in The Ruby-Throated Humming Bird in 2007 and were seen again in Piranhas! in 2011 and became an actual plot point in The Ruby Hummingbird of 2013.