TWICE has truly become mainstream since the group randomly appeared on an exam paper.
One of the questions included on an exam paper includes a small portion of the lyrics to TT.
Only two lines from the song appeared but it is obvious that the lyrics are from TWICE since the lines that were included were one of the more distinct parts of the song, which is the ba-ba-ba-baby part. And to make it even more obvious, the question also has a picture of Dahyun under the lyrics. Its unmistakable that the lyrics are from TWICE.
Take a look at a question on an exam paper where TWICE has been included: