User blog comment:FossilsDaDaDa/Fossy's 100 Picture Challenge/@comment-4037231-20110802220607/@comment-3394114-20110803193421

"How would the kids look like?", good question if you ask me. Well, let's use Fossy's theory about Ferb and we'll stick around with it. For first, Ferb isn't an alien, is a half-alien, that makes him 50% human, 50% alien. His mom race was possibly an Hopkinsville goblin or a Nordic(Aryan) alien, or something between, so Ferb would have some human traits from here as well. Okay, getting away from this, if Ferb won't marry Vanessa, it probably would marry another woman, which would be human. That will make the kids be 75% human, 25% alien. Here goes the genetics again: The alien print would be shaded, the only things at kids would be either the green hair, or the blood based on copper(being blue instead of red, as the human blood is based on iron), or the different eyes size, that would pass as a human disease(I'm talking about the "non" human characteristics, as his nose or face shape or stuff are more human). If Ferb's mom would be a Hopkinsville goblin, then would be short, but Ferb didn't get this gene, as he's one of the tallest in their group, which makes his mother likely a Nordic(Aryan) alien, but again, it would miss the pointy ears. Now, let's get some reference from Jessie. She has the elf ears, but she is tall, again making me think she's something between a Hopkinsville goblin and a Nordic(Aryan) alien. She's missing one finger, but because Ferb doesn't, it's a very low chance that a Ferb's kid would miss one finger too. I think this is the answer at your question. This informations are based on Wikipedia and the theory of the user FossilsDaDaDa. Any mistakes or misunderstandings are not the author's fault and it wouldn't affect it in any way.