Did you have it before iOS 12.2 update? On your iPhone 6?
I do not know what to say.
Use Animoji and Memoji in Messages on iPhone
In the Messages app on iPhone X and later, you can express yourself with Animoji that mirror your facial expressions. Or create a Memoji, a personalized Animoji, to match your personality and mood. You can use Animoji and Memoji in Messages conversations and FaceTime calls.
Use Animoji and Memoji in Messages on iPhone - Apple Support
https://support.apple.com/en-in/guide/iphone/use-animoji-and-memoji.../ios