Oooh! Well, Allegra has the power of latent power activation, and when she was in high school she accidentally activated another person's invisibility. There was some confusion over whether she could make people invisible or teleport them or something, but in the end it is what made them find out about Allegra's power. It doesn't have to be the only power the other person has, in fact it could be a second or third power they got afterward. :)