The screenshot from Super Mario RPG tells the whole story here! If you check the right corner of the fireplace in the room of Princess Peach (who at the time was still known as Princess Toadstool) you will find an item. In the Japanese version of the game it is called "XXX" but in the translated English copy it is termed "???" The MarioWiki has more details on this scene:
Toadstool's ??? is in between a blue chair and the fireplace in the back of Toadstool's room in the Mushroom Castle. If Mario finds it at the beginning of the game, Grandma rushes over to Mario and offers him a Mushroom if he'll mind his own business; however, this can only occur once, and before Toadstool joins the party. If they look at it after returning Toadstool to the kingdom, either Toadstool or Grandma (it is unspecified) tells Mario to return it. If Mario looks at the object after Toadstool joins Mario's party, the princess will scold the plumber, saying that he does not respect her personal, private belongings. Players cannot see the object on either occasion as Mario faces away from the player rather than towards them when he finds it.From a localization standpoint, this scene caught my attention because linguistically-speaking XXX is valid English. However, I wondered if this XXX was an example of waseieigo, a word that has English origins but differs in meaning when used in Japanese. As I am sure many people are aware, in English, XXX is typically used to refer to pornographic or explicit material. For example, the domain .xxx is used as a marker for pornographic Internet sites. But does the word hold the same meaning in Japanese? I scoured the Japanese internet for answers.