The latest versions of Apple MacOS, and iOS include a video reaction feature which allows you to use hand gestures to add animated graphics to your screen! If you've been seeing balloons, confetti, or a thumbs up bubble appear on your video you likely have this feature enabled.
Apple's informational guide on this feature can be found here.
Turn it on or off on MacOS
To enable/disable this feature on MacOS, click on the video menu icon which appears in the top right when a video call/live stream is in progress, then click on Reactions.
Turn it on or off on iPhone
To enable/disable this feature on your iPhone, swipe down in the upper right hand corner while a video call is active, and click on Video Effects.
Then, click on Reactions.