Looking at your examples, I might very well simply make that one word "wow". For example:
Mr. Y said, "Wow, you've always been late before."`
Mr. Y said, "Wow, you've always been late before."`
This is a bit of a cheat though because "wow" doesn't mean "uncharacteristically": it is an interjection indicating surprise at something that has happened. There are many other interjections that can indicate surprise; "wow" is just the one that came to mind and has the virtue of being very short and widely understood.
