That has been around for years, it's known as Baby Alive. My sister had one in the 70's. You feet it "baby food" or give it a bottle. The stuffyou feed it passes through the doll and fills it's diapers.
Yup: a neighbour kid had one in the same time period. Funny thing, it must have been too difficult for a kid to clean out properly, because it rapidly turned into an unintentional science experiment and ended up in the trash - pretty gross!
Yeah, after a few days of feeding it, it began to smell like what it was suppose to be doing in the diaper. It got pretty rank. Our mother saved my sister's doll from the trash can by giving it a water hose enama to clean it out. However it never was able to "eat" again because the mechanic shorted out when our mom did that.