Exactly what year of the Rooster said. I have quite a few purebred Ameracaunas, but they will still hatch a chick with a single comb, or no beard, quite a bit of the time. Even taking a pair that meets SoP perfectly, still gives off-traited birds. Remember that all of the chickens in the World are a mixture of other breeds, even our loved 'Brights. They all originated from the Red Jungle Fowl, which is pretty much accepted as the original chicken. That bird is a long way from a 'Bright. It's like getting a red-headed son from 2 black-headed parents. Doesn't mean anyone was "up to somethin'" hehe Hidden genes (since we can't "see 'em") can always pop-up and give you something interesting.
As a point, I currently have a 3 weeks old Bantam born in a clutch from my Barred Game hen. It's a blonde/buff and white little thing, cute as can be...BUT, there is not a buff chicken on the place except for an Orpington, that is huge compared to this lil Banty. My lightest colored Bantam is LG, a Lemon Blue Roo that is currently living with 2 blue-laced hens...go figure...the rest of my breeding-aged Bantams are SDW's, 'Brights, Blacks, and BBReds. Where did this coloring come from? The egg was left in the nest by a roving Banty hen after I let them all out for an afternoon of poops and giggles with the big gang. Everyone had fun, but what gives with this little chick? I can't wait to see what it actually feathers out as...but I've never had a chick with this coloring, so we're allw atching it closely. That is the fun of cross-breeding, to me. Ya never know what pretty bird you'll come out with.