(Don't call me sir, I'm a sergeant!)
A wonder animal can be a dog or cat (I don't discriminate here). Their bite a/o claws do 1d6-1 in close combat.
Armor Class and Damage
Dogs are AC 7. Cats are AC 6. Both animals surprise humans on a 1-3 on 1d6 if the referee choses to roll for surprise. Furthermore their keen senses allow them to avoid being surprised and warn their human companions.
(Who says a wonder dog has to be a German shepherd?)
Wonder animals can follow normal animals commands flawlessly -when they chose to. A dog ordered to go on ahead who spotted a minefield his human handler missed could stop instead and even stop his handler. If they have to display human level intelligence they must make a saving throw. They would need to do this, for example, to fetch keys off a sleeping guard's belt or enter through a window and open a door.
When a wonder animal is reduced to two hit points or less they can feign death. This will buy them a breather which lets them restore 1d4 hit points. Ordinary troops (1 HD) are automatically fooled. Higher level foes may get a saving throw.
Wonder animals get a +2 to saves vs. suppressive fire and damage caused by traps.
Level XP HD BHB ST
1 2,500 2 +1 14
2 5,000 2+1 +2 13
3 7,500 3 +3 12
4 10,000 3+1 +4 11