Three Reasons Brahma Didn’t Play Tricks On Hiranyakashipu

“In order to convince Brahma that all those cows, calves and boys were not the original ones, the cows, calves, and boys who were playing with Krishna transformed into Vishnu forms. Actually, the original ones were sleeping under the spell of Brahma's mystic power, but the present ones, seen by Brahma, were all immediate expansions of Krishna, or Vishnu.” (Krishna, The Supreme Personality of Godhead, Vol 1, Ch 13)