This really doesn’t need to be marked as mature, because ponies don’t normally wear clothes (about 90% of the population of Equestria doesn’t wear clothes normally at least), there are moments in kids TV shows where some characters are embarrassed while in their birthday suit such as Regular Show, The Amazing World Of Gumball, Fairly Odd Parents, Spongebob SquarePants, Tom and Jerry, Ed, Edd, and Eddy, Total Drama Island, etc.