Someone told me in the name of Rav Ephraim Wachsman that after the angels see how much pleasure our Pesach Sedarim give Hashem, they become jealous, which creates an element of danger for Klal Yisroel. Consequently, Chad Gadya is said to protect us from the potential negative effects of the jealousy.
What is the source for this concept? (Preferably, how does that work?)