Why do characters in One Piece have weird signature suffixes to their lines? I have seen often that characters in One Piece have their weird (read: at times irritating) signatures. Is there any specific reason for them?

For example, in the picture below, Vito has rorero as his signature. These suffixes sometimes kill the entire feel of the scene, which is why I was wondering why were they so important to have in the first place.
In One Piece, many characters are known to laugh in unusual ways by either adding to the typical "haha" or using different syllables entirely. These laughter patterns are often unique to individuals and may be based on their personalities or appearances. Some of the especially weird laughs are different in translated versions; for example, Caesar's "shurororo" becomes "shuhohoho" in the English manga. It should be noted that laughing style of "Fufufufu" or "Ufufufufu" is a common Japanese laughing style used for mature women in anime and manga. In addition, the common phrase "Arara" is not a laugh, but rather the Japanese version of "Oh my, oh my, oh my". 

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