Search your deck for a number of Energy cards up to the number of Mareep in play (both your and your opponent's) and attach them to Mareep. Shuffle your deck afterward.
In Japan, a specially stamped reprint of this card, along with five others, was awarded to those who won in Pokémon Center Card Free Battle events held at Pokémon Centers during the Autumn of 2009. Winners could only select one of the six cards available at each event.
Trivia
The Japanese promotional print has a generic Pokémon Center logo in the bottom right of the illustration window.