Memoji showing up that I have never used

My question is as such. I was sending a text message and went to add an emoji to the conversation. I noticed that frequently used memoji popped up. I have only used Memoji one or two times with the little alien guy. The rest of the board was populated with different ones with kissy faces and robots etc I have never even clicked on. Why does this happen? I prefer regular emojis and only use 4 of them so I understand that the rest of those are going to populate with random or ones used over the course of the iPhone. Is this the case with the Memoji? It backfills?