"I wish that Joy will give birth to my children, and will marry me and we will raise them together."
It wasn't a perfect plan, but it was as good as he could do. Alan couldn't wish that they would continue to be in love, since Joy had wished that that was caused by a potion and would end tomorrow.
But he could wish for something that probably would only happen if they fell in love again. And even if it happened without them falling in love, it would be such an inconvenience that Joy would probably wish them to fall in love, just so that it works out better.
Or so he thought as he put the stone down again and as he went home and fell asleep. But come the next morning, he was no longer in love with Joy--who was a good friend, but hardly a real girl--and he realized that he may have made things go really wrong....
