Freckles got put in a disposable adult diaper after returning to the motel room with Shatter (the one native to Equestria) after going out for ice cream. While Shatter took medication to help break down the dairy products in ice cream, Freckles did not. So, when they were in the motel room, Freckles had no say being put in the disposable diaper and she didn't know why, Shatter avoiding the question and answer. A couple hours later and Freckles starts getting an upset stomach and indigestion from the dairy, it was here that she started to desperately ask questions. She knew that digestion wasn't suppose to feel like this and is frantic for answers, including why she is wearing the diaper and what's it is for. Shatter is dodging those questions and didn't realize that Freckles doesn't fully know how to deal with a situation like that, so it will be a long night ahead.

Fyi, for the love of jesus, mary, and Joseph! Freckles means the cellulose of wood found in paper, and disposable diapers have that material in them.