The three videos are of Nila laughing.
Turn the volume up and listen. The video quality is bad for two reasons; the lighting was low and we were trying to keep Nila distracted from the camera. When she sees the camera, she usually stops laughing.
Angie was playing with Nila's blocks. Angie'd stack them up and knock them down. Each time she or Nila knocked the tower down, Angie would say "Kaboom!"
Nila thought it was hilarious.