Teddy suggests that Bob and Amy go on a date to spend a little time with Charlie. Later, PJ reluctantly takes Charlie for a walk in the park and meets a girl named Emma. When he comes home all happy, Teddy looks in the stroller and finds that the baby is not Charlie! So Teddy, Gabe, PJ, and the baby go to the park and look everywhere and they cannot find Emma. They decide at the end to just tell their parents about the incident. However, at the restaurant (where their parents are), they see Emma with Charlie and her family. So they have Gabe do his "magic trick" which is taking off the cover of the table and messing up everything, while Teddy and Emma quickly switch babies.
Overall, I think this was a superb episode and was written and handled very well. The only thing that makes my score not perfect is Emma not caring she has the wrong baby, or actually not even knowing she has the wrong baby. That, to me, didn't make sense.