People are familiar with only those individuals whom they see and recognize and the majority consists of those individuals whom we don't recognize.
Therefore a smart and cunning person can deceive others who don't really know him very well. However, none can deceive the Imams (a.s), because the Imams (a.s) recognize each and every one of us by our names.
Imam Reza (a.s) once wrote in one of his letter, Hazrat Mohammed Mustafa (s.a.w.a.) is the Trusted One (Ameen) of Allah among His creatures. After his (s.a.w.a.) demise, we are his inheritors and are the trusted ones of Allah on this earth. We know who among you will be involved in which examination and calamity and where you will die. We know the lineage of the Arabs. We also know who will be born on the religion of Islam. If we see someone then we immediately recognize how strong is his faith and the amount of hypocrisy in him. And we have the names of our every Shia along with the names of his father.‟ (Ibid., p. 223, tradition 1). Thus simply calling ourselves as Shias is not sufficient. Instead we should beseech Allah that our names should be included in the list of those Shias who are with our Imam (a.t.f.s.).