Croup is a contagious respiratory thing that makes your kid sound like a particularly obnoxious barking seal, but it's not serious. One of the treatments is a humidifier. Or, if you don't have a humidifier, running your shower as hot as you can and sitting in the steamy bathroom. As we have neither a humidifier nor enough hot water to allow us to run the shower unnecessarily, A. and Cubby just played with some blocks on the floor of the bathroom while I actually took my shower this morning. I don't know if it was very effective, but it can't hurt anything.
Anyway, based on Cubby's behavior--that is, as full-tilt and insane as ever--it's quite clear he's not suffering any distress. And so we will just wait out the next few days and the seal impression until Cubby is once again his impeccably healthy self.
Have a wonderful weekend, duckies!