How is horizontal gene transfer between microbes in any way relevant to a discussion about the ancestry of chickens that only reaches back to the dinosauria clade? Chickens are invariably a sub-group of the bigger group dinosaurs.

Chickens are dinosaurs in the sense that they're also tetrapods. A dinosaur is an evolutionary group in which all members have a common ancestor population that is distinct from the rest of the evolutionary tree. So too with tetrapods, isopods, primates, arachnids, etc. So anyway, it's true that birds are dinosaurs, but it's not a very useful description.

It's funny, I remember being 7 years old and thinking two things.

1. T-rex feet look very similarly to chicken feet, they must be descended from the T-Rex.

2. I'm 7, there's no way this is true.

I immediately wrote it off as being incorrect. There's no way people actually believe this right?