as far as I know, you don't have to start either of them. But they certainly help with downtime.
Krustyland is a BIG help cause of the mini game attraction Sideshow You which gives off 5 FREE donuts on ever 300th balloon popped. Plus KL and Squidport buildings give off xp that help you level up and the faster you level up the faster you get to the bonus levels for FREE donuts and Squidport buildings add to your Consumerism rating in the conform-o-meter
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