Pick any mini I said...
Easy enough to homebrew a giant frog: Might d8, Agility d4, Intellect d6, Grace d4, 4 Wounds, skin counts as light armor (d6), and can hop its full Speed (5) and also make an attack at +1d4.
I dunno if they'll give the barbarian or frog the cold iron scale armor, but I'd really like to draw the frog wearing it...
Pets are mostly going to just add dice to the owner's various Pools. This way you don't gotta spend an action to make them do stuff: if you gotta wolf, it'll add a d6 or d8 to your Attacks. If you have a dog, it could add d6 to your Attacks, and d4 to your Defense (since it's protecting you).
Of course if their master is incapacitated, they'd be able to do their own thing (though their dice wouldn't be as good as the typical character).
This already follows the Aid Another rules, in which multiple characters roll all of their dice and choose the two highest. So, if you're searching a room, instead of having everyone make their own Search check, everyone rolls their Intellect and Search dice, and goes with the two highest.
Mounts have the same thing, you just get to use their Speed. How Speed works is that you have two values, like 2/6. If you only move 2 spaces, you can still do something like attack or whatever. If you move 6, you can't do anything at all.
There's a universal Charge action, but you discard your highest Defense rolls until your turn starts, so it's a bit risky (fighters, barbarians, wolf druids, and so on can take a talent that negates the penalty, and if you rank it up can instead gain bonuses).