Well, hyenas are pretty awesome. Why else would I have chosen my username? Lions are pretty awesome too, (in fact, they're the national animal of Norway which is near Sweden, Mojang is in Sweden) and I was thinking of what both of these animals would be like in Minecraft, here are my ideas;
(side note: the reason these are intertwined is because they're pretty closely related and it seems weird to make two posts about mobs that go together)
Appearance: Hyenas come in 3 patterns, a spotted hyena, a striped hyena, and a shadow hyena. They have a general appearance of hyenas in real life, a little stocky and wolf-like (even though hyenas are more related to cats and have their own species) and with a somewhat arched back, as well as a mane and short tail. Spotted hyenas are a lightish-brown with a darker brown mane (and spots in the same color). Shadow hyenas have a similar appearance, but they're a light greyish-beige color and have a black mane and spots (they have a dark grey throat/stomach as well and also have a slightly fluffier/spikier mane). Striped hyenas are a beige-white color and have a grey-beige mane and a black stripe pattern. Hyena cubs/pups/kittens(?) appear similar to adult hyenas, but smaller. A hyena has a 1/3 of a chance of being each of these skins.
Lions are golden-beige with a dark brown mane (but some don't have manes). Lion cubs appear similar to adult lions, but smaller and without a mane. A lion will have a 1/2 chance of having, or not having, a mane.
Hyenas are about the size of a Minecraft wolf (but slightly larger). In turn, hyena cubs are a little larger than wolf pups. Lions are about the same height as an iron golem (2.7 blocks tall), but might be a little shorter.
Behavior: A hyena will be fairly social and will often try to start a pack with other hyenas if it can find any. If they don't find any hyenas, they might hang out with wolves, but this is rare and normally only temporary. Lone hyenas, however, are somewhat more common than hyenas that join wolf packs. Hyenas will start packs with any hyena, regardless of what type they are. A hyena pack is identified similarly to a wolf pack, they tend to follow each other and stick together and will also attack together. Hyenas tend to attack chickens, rabbits, sheep, pigs, cows, monsters, and might attack lions. Hyenas avoid lions if on their own, however, but might attack one if they're in a pack. Hyenas also steal food from lions on occasion, but will often avoid doing so, unless there are no lions anywhere nearby and they can't find food (but might take the risk of being attacked by a lion if no livestock or food is nearby). Hyenas also laugh a lot, but striped hyenas laugh a little less than the other types.
Lions will start a group with other lions (ocelots will sometimes join too, but this is rather rare), and will hunt for chickens, rabbits, sheep, pigs, and cows. Sometimes they might hunt for monsters too. Lone lions do happen, however, but they usually will join a group of lions if one is nearby.
Hyenas and lions will normally mind each others' business unless one provokes the other or if they try "getting" each others' food, either by physically stealing their food or by picking up meat/attacking an animal the other was going to attack. Both of them also don't bother villagers or iron golems. They also both pick up meat from the ground if they see it. Hyenas will pick up bones from the ground, however, and lions will not.
Taming: Hyenas and lions are tamable.
Hyenas are tamed by being given a bone directly. If it's on the ground, it just picks it up. After taming it, it can be told to stand or sit and will follow the player. Hyenas don't attack anything when tamed unless they are told to, or the mob attacks their owner or the hyena itself. Monsters are still scared of hyenas regardless if they're feral or tamed, but feral hyenas will chase monsters (but will try to avoid attacking creepers, they do, however, chase them away like ocelots). Tamed hyenas near a playing jukebox will "dance" (like parrots), but instead of doing a "party parrot" dance, they bob their heads up and down. The speed of their dance depends on the tempo of the song playing.
A lion is tamed by giving it fish. When tamed, they'll protect their owner and maybe a nearby village like an iron golem would (it's more likely for them to do so in savanna villages, however). Lions have higher health and attack strength than iron golems, and are faster and can even sprint, so they might be a little better as guards. Despite lions seeming to be "big meanies", they're very nice to villagers, iron golems, and players (so long as they aren't doing anything bad in the village!). They even will give a smaller sunflower to (most commonly) villagers, but might give this to iron golems and players who have a high popularity in the village as a sort of "thank you". While the sunflower is smaller when the lion holds it, it is normal-sized as an item. Instead of attacking a zombie villager, a lion will give it a sunflower, which heals it after 0-5 seconds.
Breeding: Both of these animals, feral or tamed, can be bred.
Hyenas are bred by giving two hyenas a piece of meat of any type. Both hyenas must be standing to successfully breed, however. Regardless of the type of hyena, they can all breed. The type of hyena pup generated is normally one of their parents (two striped hyenas would most likely create a striped hyena pup, or a shadow hyena and spotted hyena would most likely either create a spotted hyena or shadow hyena pup), but there's a decently low (1/100 chance) of the type of hyena being ignored and just choosing a random one.
Lions can be bred with any meat as well. Since animals in Minecraft don't have genders, they can be bred regardless of whether or not they have a mane. However, it is possible (albeit rare) for a lioness to have a mane, or a male lion to not have a mane.
Biome: Most commonly they're found in savanna and related biomes. It's also possible for them to live in jungles, but usually uncommon.
Hostility level: Both are neutral and tameable.
Health and attack damage: Hyenas have a health of 20 (10 hearts) and attack damage of about the same as attacking with an iron sword.
Lions have a health of 120 (60 hearts!) and attack strength of 6 on easy, 9 on medium, and 12 on hard.
Immune/resistant to: Hyenas and lions can not take fall damage. Lions also have very high health and damage strength.
Drops: Hyenas, upon death, will drop 1-3 EXP. They also drop 0-15 pieces of meat of any type. They'll be raw even if the hyena died while on fire.
Lions drop 3-8 EXP and have a chance of dropping 0-2 emeralds due to their connection with villagers and usually will drop 0-4 lion teeth which can be made into a potion of strength (since they're very strong) and might drop a sunflower upon death as well.
Easter eggs: Naming a hyena "Banzai" will result in the hyena becoming a shadow hyena with a shorter mane and having yellow eyes, similar effect goes with naming a hyena "Shenzi" (which results in the hyena also being a shadow hyena with yellow eyes, but the mane is longer) or "Ed" (which results in the hyena being very similar in appearance to "Banzai" but with more "googly eyes" and has his tongue out when he opens his mouth. "Ed" also laughs more than any hyena and is less serious as well)
Naming a lion "Simba" or "Mufassa" will give it a reddish-brown mane and more golden fur. One named "Nala" will give it no mane and tan-beige fur. If it is named "Scar", it turns brown with a black mane, green eyes, and a scar on its left eye.
Of course, these are all references to "The Lion King".
Sounds: Hyenas will usually laugh, growl, or make "whoop" sounds (a little like howling wolves!) like they do in real life. They also yelp when hurt or killed.
Lions make similar sounds to iron golems, but in a lower and more growl-like pitch. They also roar or purr (the latter can be taken from normal Minecraft cats, but in a deeper pitch) from time to time.
So, tell me what you think and feel free to tell me what I should add or change or whatever, just keep it polite and well-reasoned.
You lost me at the ability to tame them.
Both these animals are feral and almost impossible to domesticate.
There is no reason a lion should be as tall as an iron golem and have more health.
The thing that bothers me the most are the drops these mobs have.
Why would a Hyena drop up to 15 pieces of meat?
What "connection" do lions have with villagers?