I just saw It (2017), but haven't read the original book yet. In the opening scene, Pennywise lures Georgie into his sewer by acting friendly and making him laugh. It's not until Georgie reaches his arm into the sewer does Pennywise bite his arm off.
This behavior is a lot different compared to the rest of the movie, where Pennywise scares the other kids psychologically as much as possible before capturing them.
Why did he act so much more friendly to Georgie before hurting him?