Prince Louis smiled and waved at this year's Trooping the Colour in honor of his grandfather King Charles' birthday.

The 6-year-old prince, who was enjoying a covered carriage ride in the royal procession, gave a small wave to onlookers, the BBC reported. Prince Louis waved as the "carriage portion of today's event" neared its end and the family was preparing to head to the Horse Guards Parade, the outlet reported.

The prince made his first public appearance since his siblings, Prince George and Princess Charlotte, and his mother, Kate Middleton, who made her first public appearance since undergoing scheduled abdominal surgery in January and later announced she had been diagnosed with cancer and was undergoing preventive treatment, shared the ride in the Glass State coach.

Prince Louis seemed friendly to the royal onlookers and attendees, but his sister Princess Charlotte gave fans a, um, different look.

At her grandfather King Charles' annual birthday event, the young princess gave a look that mercilessly struck a chord with royal conspiracy theorists who have been absent from the public eye since the whale princess was hospitalized: "Don't test me. Don't test me. Apparently, like the royal household and her father, Prince William, the young princess has had enough of the ridiculous gossip.

Conspiracy theories surrounding Kate Middleton's health, her position within the royal family, and even her marriage to Prince William reached a fever pitch after she was hospitalized in January.

Since the palace announced that she would not return to public life until the fall (at the earliest), the palace has reportedly been doing its best to avoid another conspiracy theory fiasco.

The day before King Charles' birthday celebration, the Crown Princess announced that she would make a surprise appearance at the event. She said, "I look forward to attending the King's birthday parade this weekend with my family, and I hope to attend several public functions throughout the summer. I am learning how to be patient, especially with uncertainty," the Princess of Wales wrote in a statement shared on various Kensington Palace social media accounts.

"I am taking it one day at a time, listening to my body and allowing myself to take the time I need to heal."