I've been thinking more about this... especially the one with a little crest popping up.... I assume you were hatching only Isbar eggs. IF the Cream Legbar did manage to be the daddy, the chicks would have been barred (if he is double barred as he should be to produce autosexing chicks). So this crested baby could not be from him. It may be genetics from a mix up earlier down the line I suppose.
Now if you were hatching both Isbar and Cream Legbar eggs, is it possible a Cream Legbar female was mated to an Isbar? Cream Legbar females only pass a barring gene to their sons, so a female offpsring will be nonbarred and probably crested.
Nope. I was hatching only Isbar (or what I thought were Isbar) chicks. I currently have some Lemon Cuckoo Orphington x Pure Ameracauna and they are the fluffiest, cutest things I've ever hatched! (I'm doing an olive egger project). I think they should be called "super puffs"!
Chicken genetics are very fascinating. Other than the puffiness, these 2 do not have any coloring at all like their parents. Hen is solid black pure Ameracauna and rooster, of course is lemon cuckoo orp (English). Chicks look like they will the brownish!