In ancient times, people believed hares were hermaphrodites that could give birth without compromising their virginity. This idea led to an association with the Virgin Mary, and that’s why we have bunnies at Easter. Source
That’s one explanation but it’s not the only one.
In one of the Germanic religions, a goddess saw a bird suffering in the cold of early spring, its wings frozen so it couldn’t fly. She took pity on it and turned it into a rabbit. For some reason, though, it still laid eggs.
The best explanation for rabbits at Easter is that they were the animal of the pagan deity of fertility, estar, for whom the holiday is named after