Bitmoji Face Expressions

Hello, I see Snapchat accounts that have Bitmoji (I think that's what it's called, it looks like us) whose facial expressions change constantly. Do these expressions change automatically? If not, it means that the Snapchatters in question are on Snapchat all the time.
Do the expressions reflect the mood of the snapchatter and change according to their moods automatically (without being done manually)?
For iOS users.

Configuration: Android / Chrome 76.0.3809.111