Hi, 

This appears to be a dried and dead frog. If you have a pet, maybe a cat, it could have brought it inside, or it came in through a small opening in the house and couldn't find its way back out or to water and dried up. 

It shouldn't be a problem or a common occurence, but you can look for any areas like a sump pump drain or similar, or other areas where it could have gotten inside and try to seal those up. 

Let us know if you have other questions. 

Emily