Sending an invitation to the Royal castle to Prince Blueblood is a simple trick of the light. Since Pinkie Pie knows how to word and write it all, there is no telling the fake from an actual invitation.

A Prince is to know and appreciate the finer things in life, the visit to the SPA should go along. Escorted by a high guard sounds legit enough to him.

Unbeknownst to him, it is Pinkie Pie orchestrating the show, instructing the guards to take turn to wait for the Prince. Of course she knows her treats and SPA, never forgetting a single detail.

Just how resilient the Prince is to the humiliating adversities, as he discovers what he did not expect to be there, deep within him.