Do you mind your Ps and Qs?

Today’s English
27.1.2017
If you want to warn somebody to be careful about their behavior and words (because you don’t want any unwanted behavior from them) you can ask them to mind their Ps and Qs.

1.Mind your Ps and Qs Preethi, don’t talk like this anymore.
2.Please mind your Ps and Qs before talking to our principal. He expects respect.

Another expression related to it is “Out of character"  that you use when you see unusual behavior from someone.

1.Anandhi, what happened to you? It seems, you are out of character today.
2.I don’t expect this from you.  Why are you totally out of character today?

(Creative people think out of the box and often behave abnormally.  Do you mean, they are out of character? )