One of the things that keeps me interested in the Harry Potter's Puzzles and Spells is the games within the main game. Some are special events. Others are seasonal. One that popped up recently was the Broom Race. Which isn't a game itself, but rewards prizes based off of the game wins within the main game.
In this case, I ranked in second place. Which offered a nice little bonus for a game I was going to play anyway.
I am not a game developer, so I find it interesting to see these types of games within games pop up unexpectedly when I open up the app to play.