Gravelord Azir mimicking opposing character's voices?

Check out the video link.

Not sure if its skin-specific, and unfortunately, this is the only instance of this that I managed to record, but he did it every time he attacked. The voice he mimicked changed between Karma, Vayne and Lissandra. Interestingly, I don't think he ever copied my Cho'Gath.

Is this a one-off, or has anyone else experienced this?