Instructions
Sit down at one of the slot machines in Veilstone City and start playing. While playing normally, watch the bottom of the screen for a shaking Pokeball. Eventually Clefairy will pop out.
Stop the reels quickly to get "777" or "GGG" to enter Clefairy Bonus mode, which is necessary to get Bonus replays.
Stop the left, center or right reel with "Y," "B," or "A" the instant Clefairy points to one of those reels. When you do this, you will get "RRR" every time for a Bonus Replay. Get 10 of these in a row and return to the counter to redeem your coins for "TM Explosion."