Answer:
There is a "time freeze" effect in the Poptropica Store. It sells for 250 credits, but can be used free by paid monthly members.
Once you buy or access the item, select the item card from your Store Items and "PUT ON". When you activate the device, all motion in the background or by the characters comes to a stop. This is only valuable to observe moving features, and does not affect game play in any way.