Potty Training Regression
Both Mason and Audrey "regressed" when they realized they were in complete control of their bathroom habits. Mason would pull his pants down, then say "Hey Mom! Look what I'm doing!" before starting to pee ON something. This happened for him about 2 days after we had finished the 3 day potty training method (he was great for 2 days, then we spent a day and a half of him trying to pee on things and then he was completely great).
Audrey realized she could "hold it" and wait to pee and tried testing her limits which led to some regression. For Audrey, that happened about 2-3 weeks after her 3 day potty training, and it only happened a few times before she was back to just taking a break and going potty when she needed to.
Some children can have a much more serious regression, especially if there is a big change in their lives such as a new sibling, a new daycare/school, a parent leaving for vacation, business, or divorce or other BIG changes