One of the reasons given by Chazal for why the Shabbat just prior to Pesach is called Shabbat Hagadol is that this is the day the Hebrews brought the Passover lambs into their homes and the Egyptians did not take retribution against them.
Pharaoh summoned Moshe and Aharon and said, "Go - bring offerings to your God in the land." Moshe said, "It is not proper to do so, for we will offer the deity of Egypt to Hashem, our God - behold, if we were to slaughter the deity of Egypt in their sight, will they not stone us?"
As we all know, Pharaoh did not let the people go and the lambs were taken into the Hebrews' dwellings for four days until the time came to slaughter them and roast them whole over an open fire for all the world to see and know that Hashem is God over all.
Can you imagine the sound of the bleating up and down all the streets? This was quite an in-your-face insult to Egypt, but they bore it without repercussion and Chazal considered it a miracle. Hence - Shabbat Hagadol.
This is also where I point out that the "Hebrew-roots" xians, including the messianiacs (not misspelled) claim that Yeshu is their "Passover Lamb" without an inkling of what that really means. But, it's true enough - false god of spiritual Egypt.