ectypal.net

...Christians gathered every week to celebrate what they called a “love feast.” This was done in private, and only the initiates (those who had been baptized) were admitted. Furthermore, Christians called each other “brother” and “sister,” and there were many who spoke of their spouses as their “sister” or “brother.” Joining these known facts, non-Christians imagined Christian worship as an orgiastic celebration filled with Christians eating and drinking to excess, then extinguishing the candles, and venting their lusts in indiscriminate and even incestuous unions.

Communion also gave rise to another rumor. Since Christians spoke of being nourished by the body and blood of Christ, and since they also spoke of him as a little child, some came to the conclusion that, as an initiation rite, Christians concealed a newborn in a loaf of bread, and then ordered the neophyte to cut the loaf. When this was done, they all joined in eating the warm flesh of the infant. The new initiate, who had unwittingly become the main perpetrator of the crime, was thus forced to remain silent. Such rumors were made more credible because it was commonly known that when Christians found an abandoned infant they would pick it up and take it home with them.

Some even claimed that Christians worshiped an ass. This was an old rumor about Judaism that was now extended to include Christians, and make them an object of mockery.