Las tres mellizas y El fantasma de la Ópera is the story about triplet sisters. The creator is Roser Capdevila (Barcelona native and artist), who gave birth to her own triplets in 1969. So she decided to write stories about three sisters and make illustrations for them. Triplets have lots of adventures inside fairy tales and classic stories - including story about the Phantom of the Opera.
There are actually two editions: an episode in animated series and its novelization. Even with three little sisters from modern world, this story is very close to the original novel.
So you can see more screenshots from the cartoon here.
And more pictures from the book here.
I SAW THIS EPISODE WHEN IT AIRED ON THE TV I WAS LIKE 10 IT MADE ME SO SAD POOR ERIK :(
(This was before reading the book of course)
Context: the triplets are frenemies with a witch that teaches them lessons by magically sending them into books, but they include shakespeare tragedies and stuff like that. The day of the Steadfast Tin Soldier I thought my heart would break in half oh my god nope