[out of character] {adv.}
or {adj. phr.}
1. Not in agreement with a person's character or personality; not in the way that a person usually behaves or is expected to behave; not usual; unsuitable; uncharacteristic.
* /Mary is a nice girl. Her fit of temper was out of character./
2. Not in character; unsuitable for a part or character.
* /It isn't always out of character for a young actor to play an old man, if he is a good actor./
Contrast: IN CHARACTER.