Yes, a creature with summoning sickness can be tapped to pay the cost to saddle another card
This particular Eevee card is a Secret Rare, which means that its an alternate art variant of another card in the Terastal Festival set, and the card number goes above the main sets numbering (in this case, its card number 224 of 187)
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In a vacuum, I totally agree with my fellow writers that this card is exceptionally powerful and well-designed and deserves a spot among the best artifacts of the format
There are two targeted removal spells that cost two at instant speed (Disenchant, Terror) card draw (Braingeyser), recursion (Regrowth) and you can make a Dragon
Fun fact: Mantine can sense electrical currents in the water, helping it navigate through stormy seas