If Pepper Ann premiered in 1997, then the date which this episode flashbacks to must be some time in 1990.
In this episode it shows Nicky (in kindergarden of course) giving Milo her hat (which is the one he wears to this day) but in Crunch Pod, Milo said that he found his hat in the garbage.
Pink-Eye Pete: It's not germs! The doctor said it's a temporary bacterial infection. It'll be gone in two weeks, tops!