Werechihuahua

Shapechanger. The werechihuahua can use its action to polymorph into a chihuahua-humanoid hybrid or into a chihuahua, or back into its true form, which is humanoid. Its statistics, other than its AC, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Keen Hearing and Smell. The werechihuahua has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Savage Attacker. Once per turn when you roll damage for a melee weapon attack, you can reroll the weapon’s damage dice and use either total.

Pack Tactics. The hyena has advantage on an attack roll against a creature if at least one of the hyena's allies is within 5 feet of the creature and the ally isn't incapacitated.

Annoying Bastards. Werechihuahua's get an advantage on all grapple attacks made on creatures larger than them. They also get to use their dexterity modifier for grappling checks. 

Multiattack. (Humanoid or Hybrid Form Only). The werechihuahua makes two attacks: two with its dagger (humanoid form) or one with its bite and one with its claws (hybrid form).

Bite (chihuahua or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d6 - 1) piercing damage. If the target is a humanoid, it must succeed on a DC 12 Constitution saving throw or be cursed with werechihuahua lycanthropy.

Claws. (Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 7 (1d4 + 4) slashing damage.

Dagger (Humanoid Form Only). Melee or Ranged Weapon Attack: +4 to hit, reach 5 ft. or range 20/60 ft., one creature. Hit: 5 (1d4 + 4) piercing damage.