Few anime characters display the same personality traits at all times, but not all of them change drastically. In some cases though, the change can be pretty stark. One type of character whose personality does a complete 180 are chilled out, nice anime characters who get serious when they have to deal with conflict.
One example of this trope is Hatake Kakashi of Naruto, who is normally a laid back dude who goes totally serious when fighting against enemy ninja. There's also Rimuru Tempest of That Time I Got Reincarnated As A Slime, who faces everyone and everything with a smile until he's actually staring down somebody who means him harm. Nezuko Kamado of Demon Slayer might be the cutest thing ever, but if you touch Tanjiro she's a force to be reckoned with.
Which of these variable characters do you like? Be sure to vote up your favorites!