You don't have to use the iPhone's Animoji feature to send animated clips - you can also pose your own stickers with it

Hit the Animoji 'monkey' button above the top row of the keyboard and pick the character you want to use

Pose an expression. When you have the one you want press and hold the image, then drag it onto the message

You can add multiple Animoji stickers to a message - just pose another and drag it on