I have a few ideas for hybrids.
A hippocampus bred with a capricorn could get a Chalicocampus. Chalicotheres are an extinct group of perissodactyls (Odd-toed ungulates) that looked like a cross between a goat, horse and gorilla. Imagine a chalicotherium with a koi tail, now!
Then, we can have hippocampi breeding with hippogryphs to get us gryphcampi. A gryphcampi would have the tail of a hippocampus, and the upperbody of a hippogryph. This, combined with the above suggestion, would tie together the 2 biggest magistream families, the Gryphon-Phoenix family and the Manticore-Ibex family.
Adding on to this megafamily, winged cats and talvars can get us dwarf gryphons, which can further be bred with phoenixes for fire/ice dwarf gryphons, and add minicorns to the mix to get us dwarf hippogryphs! And if you really wanna get crazy with this, perhaps capricorns can breed with dwarf hippogryphs to get us dwarf gryphcampi! There, that's already a whole family branch.
Adding on to the minicorns, a pinto minicorn wouldn't hurt. Also, bred with the pegasi, would get us alicorns, which are unicorn/pegasus hybrids.
Let's throw in puvias just for the heck of it. Puvias can breed with gryphons, hippogryphs, pinto pegasi and chimeras to get us rainbow variations of each. I think hippogryph/puvias should be called "Spectrum Hippogryph" to stick with the theme of space and stuff like that.
Melanistics could be introduced, adding melanistic nandi bears and direwolves. Also, a direwolf and a nandi bear could breed to get a bear-dog. Bear-dogs are an extinct group of carnivorans (Meat-eating mammals including dogs, cats, bears and weasels) that look how their name describes them. Of course, they would have their own albino and melanistic form.
Back to the melanistics, direcores could inherit albinoism and melanism from their direwolf ancestors.
Also, nandi bears could breed with manticores to get us nandicores, which are essentially flying bears. And you gotta admit, a flying bear would be freakin' SWEET.
Moving away from the megafamily, let's expand the Kraken-Ice Octopus family.
Narwhals and krakens could get us some sort of "Krakwal". Krakwals would have the general layout of a narwhal, but in place of the tailfin would be 8 kraken tentacles. Maybe one of those frills that krakens have could be on it's head, too.
Lakirian platypi and krakens could get an even more interesting result. The resulting "Platykraken" would have 8 long tails and a tuft of fur shapes like a kraken frill on it's head.
Through the narwhals, we could expand and add caeralises to the mix, breed a narwhal and a caeralis to get a beluga. A beluga is a white whale that live up north.
Inevitably, however, all things must connect, so we link the MegaFamily with the newly expanded Kraken-Narwhal family.
A kraken with a hippocampus would simply give us a krakencampus. A hippocampus with 8 tentacles instead of a tailfin.
Also, a kraken with a capricorn would get a caprikraken, which is just a capricorn with 8 tentacles instead of a tailfin.
Perhaps as a genetic mutation, chalicocampi could have their tailfins disappear, resulting in a normal chalicotherium.
Cehual boars could breed with nandi bears to get us an entelodont, which is a group of extinct carnivorous pigs.
An ice gryphon and a white tundra tylluan could result in a snowy owl-faced ice gryphon. Perhaps the same could also be said for the dwarf ice gryphon.
A direwolf and a tenera dog could result in a tenera bulldog, which would look similar to a real bulldog but with a golden mane, red legs, and on it's torso the usual direwolf coloration. The jade orb would rest in the fat fold on it's back.
Wow, that's a long post.