Why do you think it is good? A good pichu would be with a jolly or timid nature and go to the Iv checker to see if it has good IVs, because the IVs are hidden. You have to ev train in order to get EVs. To tell if it has perfect IVs in every stat, the person would say every stat is good and say it can't be better in that regard. This is not rare, a rare would be a good nature you want, perfect IVs, and shiny. A brave nature and capable of taking hits would be common, but the IVs might not.