What is the name of the loyal sidekick to the hottest selling toy?

Answer 1

That greatly depends on what the hottest-selling toy is at the time.

It also depends on the definition of "hottest-selling."

1) It's selling like hotcakes; it's flying off the shelves. Though I suppose the sidekick to hotcakes would be syrup. Or butter.

2) It heats up when it's sold. I may be thinking of a different definition of "toy" than you are. (Then again, maybe I'm not.)

3) It gets sexy when someone buys it. Though the simple act of purchasing anything can make someone (or his/her purchase) seem sexy, depending on what you're into. Like perhaps the toy from point #2.