This quote comes from the movie ‘Red, White & Royal Blue’. The movie is based on a novel of the same name written by Casey McQuiston. | Red, White & Royal Blue is produced by Amazon Studios
Movie vs. book
Henry’s description of himself being “as gay as a maypole” is used much later in the book, when he talks to Philip (his brother) while his whole (royal) family is present (Alex included).
Meaning of “Gay as a maypole”
This phrase can be explained in multiple ways. Maypole is a tall pole that is erected on celebrations of May Day in many European countries. So Henry’s phrase could express the happiness that comes with the celebration of May Day. It could also come from the fact the maypoles are decorated with colorful ribbons – using all the colors from the rainbow.