She has everyone share their body heat

"Everyone, take your clothes off," Margaery instructs the people in the carriage.

You are taken aback. You stutter "E-excuse me, Your Grace?"

Queen Margaery merely grins and says "We can keep warm if we share our body heat with one another. To do that, we will require skin contact. This method will not be nearly as effective if our clothes are on."

"She speaks the truth," Queen Talisa agrees, "While a blanket may be effective to shield one against the cold, another's body heat is even better-suited to the task."

"If you say that, my dear, then it must be true," Lady Catelyn tells her daughter-by-law.

The Volantene healer chuckles and mutters "Thank you, Mother. Now, you all heard Queen Margaery. Get down to your smallclothes."

Catelyn, Margaery, Mira, Sera, and Talisa proceed to get undressed. They set their gowns and tunics off to the side, but they keep their smallclothes on, and they hold on to their cloaks to conceal their breasts.

You are hesitant to do the same as the ladies. As far as you know, Queen Talisa is not aware of your padded state. As excited as you are to see five gorgeous highborn women half-naked, you do not think it is worth revealing such a personal and compromising secret.

"Your turn, Brynden," Margaery declares. It appears you have ****. If you want to stay in this carriage, you will have to strip and reveal your diapers to Queen Talisa. Your only other option is to go back outside. Of course, it is quite possible the ladies will not let you leave even if you want to. That does not mean you cannot try to, though.