Lying about Santa Claus is no trivial matter...
It is very sad that self-professing Christians will toy around with the idea of Santa Claus and participate in the tradition of lying to their children that Santa Claus really does exist. Many folks today seem to miss the point that all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death. (Revelation 21:8) This lie regarding Santa includes the notion that he knows if you've been bad or good. This is supposedly is in regards to everyone.
There is only one who is all knowing (omniscient) who could be able to do such a thing.
To set the record straight the only being in all of creation that can do this, who is omniscient, is God.
To even pretend that there is another is the epitome of the worst form of sacrilege.
It is antichrist through and through.
Imaginations are not a sin free zone where we can dream up whatever fantasy we desire.
We are told that we should be "casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ". 2 Corinthians 10:5
Here are couple of scriptures that explain the truth that God alone knows everything about us.
O Lord , thou hast searched me, and known me .  Thou knowest my downsitting and mine uprising, thou understandest my thought afar off.  Thou compassest my path and my lying down, and art acquainted with all my ways.  For there is not a word in my tongue, but , lo, O Lord , thou knowest it altogether.  Thou hast beset me behind and before, and laid thine hand upon me.  Such knowledge is too wonderful for me; it is high, I cannot attain unto it.  Whither shall I go from thy spirit? or whither shall I flee from thy presence?  If I ascend up into heaven, thou art there: if I make my bed in hell, behold, thou art there .  If I take the wings of the morning, and dwell in the uttermost parts of the sea;  Even there shall thy hand lead me, and thy right hand shall hold me.  If I say, Surely the darkness shall cover me; even the night shall be light about me.  Yea, the darkness hideth not from thee; but the night shineth as the day: the darkness and the light are both alike to thee .  For thou hast possessed my reins: thou hast covered me in my mother's womb.  I will praise thee; for I am fearfully and wonderfully made: marvellous are thy works; and that my soul knoweth right well.  My substance was not hid from thee, when I was made in secret, and curiously wrought in the lowest parts of the earth.  Thine eyes did see my substance, yet being unperfect; and in thy book all my members were written, which in continuance were fashioned, when as yet there was none of them.  How precious also are thy thoughts unto me, O God! how great is the sum of them!  If I should count them, they are more in number than the sand: when I awake, I am still with thee.  Surely thou wilt slay the wicked, O God: depart from me therefore, ye bloody men.  For they speak against thee wickedly, and thine enemies take thy name in vain.  Do not I hate them, O Lord , that hate thee? and am not I grieved with those that rise up against thee?  I hate them with perfect hatred: I count them mine enemies.  Search me, O God, and know my heart: try me, and know my thoughts:  And see if there be any wicked way in me, and lead me in the way everlasting. Psalm 139:1-24
For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.  Neither is there any creature that is not manifest in his sight: but all things are naked and opened unto the eyes of him with whom we have to do. Hebrews 4:12-13
God is truth.
Santa is a lie straight from the pit of hell. Why would you even flirt with the idea?