Gru's astonishment upon discovering that Wild Knuckles faked his death (and excitedly saying that he can't wait until he can do it too) may foreshadow how he later assures Lucy Wilde in Despicable Me 2 that Eduardo Perez was El Macho. Given how his idol faked his death, Gru already considered the possibility of El Macho doing the same not so far-fetched.
What would make a nun turn to a life of villainy? And at one point, she prays and levitates while an angelic choir sings, which implies this isn't just a silly gimmick and she actually has the power of God and Christ on her side. Sure, it was a joke, but that raises some unsettling questions.
I think she was once a very talented nun who enjoyed their job. However, after a few years she became bored about it and quit. When she quit, she broke the trust of her fellow nuns because they were dedicated to their job and had no desire to quit. She was then confronted by some hypnotist who accidentally put a spell on her that would cause her to be destructive and that ultimately impressed the Vicious Six enough to recruit her as a member.
Perhaps a simple explanation is she has a Tractor Beam installed in her vehicle.
A rat can lives up to three years: that means the Vicious 6 could have been already deceased during the events of Despicable Me.
Due to Wild Knuckles being implied to be deceased in the Despicable Me movies, he never got the chance to meet Gru's adoptive daughters (Margo, Edith and Agnes) nor his wife (Lucy Wilde herself).
Given that Master Chow is an elderly woman, it's likely she's no longer alive, as well, in the Despicable Me films.
