It looks like Google is testing five effects at the moment, including one that shows your face through the window of a cartoon airplane before the flies away. The balloon effect puts flying balloons in front of and behind you, while another puts a fireworks display right in your living room. There is also a confetti effect and an angel filter that gives you a halo and a pair of wings. The halo can follow your head around, just like Snapchat's face filters.
XDA says it was only able to access the effects through the messaging app's camera and that they were available through the standalone camera app. While the animated messages could reportedly be sent by SMS or MMS, the feature will go well with Google's RCS rollout, which will give you the ability to send and receive high-quality media and get read receipts in the Messages app, among other things. As with any experimental feature, it may take some time before it becomes available to the public. When it does, we hope you're ready for a jump or snap-like animations flooding your messages.