Mrs. Hasagawa is watering her vegetables innocently one morning, when she activates Experiment 613, an experiment that is designed to destroy buildings with it's sonic blasts.
Lilo and Stitch are hot on it's trail, when it yarps, and because of Stitch's super hearing, Stitch is temporarily deaf.
So, when Jumba says only someone with no ears could be safe from Yaarp, Pleakley is on the stage as an Experiment Hunter.
Pleakley catches Yaarp, but Stitch's plan to deter Gantu away from the hunt goes wrong, and he captures Stitch.
And now he is offering Lilo a trade: Stitch for Yaarp.