Get the HUB and just let it go.
Although, being my tactical self, I feel compelled to offer a battle plan if you're really terrified.
If your kid is under 10, just let it go, it'll pass.
If your kid is over 10, get (or at least act) super surprised and excited when the show is on and watch it with him. If this doesn't work, take him to wal-mart and make sure everyone within 3+ aisles knows you're there to buy your son pony toys. You'll either eliminate the fascination, or secure his loyalty for life. It's a Win-Win!!! 
-Huzzah!
