注音符號 (Zhùyīn fúhào) aka Bopomofo

See https://en.wikipedia.org/wiki/Bopomofo for more info. As I said, this
is only used in Taiwan, primarily for pedagogy and phonetic input methods.
It is possible it may be used in television subtitles aimed towards young
audiences in learning programs, but I have no direct knowledge of such
usage either way.