Where Datenshi states "It's not that I won't, but that I can't", from her music video. (She's an angel who's afraid of flying.)
Takaoka-sensei from Assassination Classroom replies "It's not 'I can't', but rather 'I will'" (from a scene in vol 5, ch 39 after beating up a student for saying he can't do something).
Apparently, the threat worked and lead to the happy end in post #7498675 .
