Emoji can be imprinted on AirPods with Apple's free message engraving service
Apple can engrave your favorite messages and emoji on products such as iPad and iPod touch.Free message engraving”Service. Engraving is possible only for some products and is not available for iPhone etc., but emoji can now be engraved on the AirPods case.
Apple Now Allowing AirPods Charging Cases to Be Engraved With Emojis-MacRumors
Apple now lets you engrave a poop emoji on your AirPods case-The Verge
Apple's message engraving service has been able to engrave characters on AirPods charging cases, but now emojis can also be engraved. Only a limited number of emoticons can be engraved on the AirPods charging case, including 31 facial expressions, hand signs, hearts, stars, animals, poo, etc.
However, you cannot engrave both emoji and text on the charging case, and you must choose one or the other. Also, the characters engraved on the charging case are significantly larger in size than before.