1To take the form of something else (especially a spirit, fox, raccoon dog, etc.); to transform oneself into another shape (often human).
昔話では狐が人に化ける話が多い。
In folktales there are many stories of foxes transforming into humans.
夜になると山の木が化けるという噂がある。
There is a rumor that the trees on the mountain take on strange forms at night.
子どもが鬼に化けてハロウィンを楽しんでいる。
A child is dressed up as a demon and enjoying Halloween.
2To disguise oneself as; to take on another appearance or persona (as a disguise).
刑事は覆面をして泥棒に化け、張り込みを続けた。
The detective put on a mask and disguised himself as a thief, continuing the stakeout.
彼女はメイドに化けてパーティーに入り込んだ。
She disguised herself as a maid to get into the party.
イベントではみんなが好きなキャラクターに化けて写真を撮っていた。
At the event everyone dressed up as their favorite characters and took photos.
3To change radically; to metamorphose; to turn into something quite different (often unexpectedly).
あの小さな会社が数年で有名ブランドに化けた。
That small company transformed into a famous brand in just a few years.
アイデア次第で古い商品が全く違う価値に化けることがある。
With the right idea, an old product can turn into something of completely different value.
地味だった彼の作品が最近急に化け始めた。
His previously plain works have recently started to change dramatically.
4To improve unexpectedly and dramatically (used for actors, artists, athletes, etc.); to come into one's own.
新人だった彼がこの映画で完全に化けた。
He was a newcomer, but he completely came into his own in this movie.
今シーズン、彼女は化けてチームの得点源になった。
This season she has suddenly improved and become the team's scorer.
練習を重ねて選手が化けるのを見るのは楽しい。
It's gratifying to see a player suddenly improve after a lot of practice.