Farts
...and then there are those that are just too polite.
some years ago when our oldest grandson was about 5, he was visiting us from Kentucky and had gone to use the bathroom. My wife happened to walk by and heard him talking in the bathroom. She knew there wasn't anybody else in there so she stopped and listened at the door. All she heard was, "'Scuse me. 'Scuse me. 'Scuse me."
It turned out his other grandma, who he was living with at the time, had told him he needed to excuse himself whenever he farted (she would NEVER use that word). So each time he did while sitting on the toilet brought out another, "'Scuse me."
When he came out we explained he didn't need to do that while alone in the bathroom.
He's now 16 and is still very polite...but no more talking in the bathroom.