The plot of a number of indifferent cards changing to duplicates of another card dates back at least to Hofzinser. In the third version of his famous “Everywhere and Nowhere,” Hofzinser changes an apparently random number of cards to duplicate Kings of Diamonds. This version appeared on p. 161 of Ottokar Fischer's Kartenkünste (1910) and then later on p. 141 of Samuel H. Sharpe's 1932 English translation, Hofzinser's Card Conjuring. Hofzinser's routine used misindexed cards showing an indifferent court card on one index and the Kind of Diamonds on the other.
Jump forward over half a century from Hofzinser's performances and we get to Brother John Hamman's routine “The Mystic Nine.” In this effect, nine ungimmicked black cards change to match one red card. The effect then takes an unusual twist wherein the performer ends up with five red and five black cards. This routine was published in The Card Magic of Brother John Hamman (Paul Le Paul, 1958, p. 40).
Peter Kane's routine, “Watch the Ace!” was originally published in the April 1962 issue of Hugard's MAGIC Monthly, Vol. 19 No. 8, p. 89, described by his confidant Gus Southall. In this effect, eight indifferent cards and one Ace are shown. The indifferent cards then change to Aces. Kane's method was simple: four double-faced cards and a Hamman Count did all of the work. The structure of the routine is somewhat similar to Brother John Hamman's routine. It was Kane who introduced the idea of using double-faced cards; an advancement that has remained in the majority of versions since.
The name “Wild Card” comes from Frank Garcia's unauthorized, marketed variation of Peter Kane's effect. Harry Riser reports that he was at Lou Tannen's magic shop in New York City when Frank Garcia was reading Peter Kane's handling in Hugard's magazine. He then showed the routine to Lou Tannen and they marketed it under the name “Wild Card.” Garcia later credited Peter Kane for the creation of the effect in his 1977 paperback Wildcard Miracles, p. 9.