Amoeboid Changeling

Changeling (This card is every creature type.)
{T}: Target creature gains all creature types until end of turn.
{T}: Target creature loses all creature types until end of turn.

Riverfall Mimic

Whenever you cast a spell that's both blue and red, this creature has base power and toughness 3/3 until end of turn and can't be blocked this turn.

Metallic Mimic

As this creature enters, choose a creature type.
This creature is the chosen type in addition to its other types.
Each other creature you control of the chosen type enters with an additional +1/+1 counter on it.

Sprite Dragon

Flying, haste
Whenever you cast a noncreature spell, put a +1/+1 counter on this creature.

Feywild Visitor

Commander creatures you own have "Whenever one or more nontoken creatures you control deal combat damage to a player, you create a 1/1 blue Faerie Dragon creature token with flying."

Professional Face-Breaker

Menace
Whenever one or more creatures you control deal combat damage to a player, create a Treasure token.
Sacrifice a Treasure: Exile the top card of your library. You may play that card this turn.

Mothdust Changeling

Changeling (This card is every creature type.)
Tap an untapped creature you control: This creature gains flying until end of turn.

Ganax, Astral Hunter

Flying
Whenever Ganax or another Dragon you control enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Choose a Background (You can have a Background as a second commander.)

Universal Automaton

Changeling (This card is every creature type.)

Shape Stealer

Whenever this creature blocks or becomes blocked by a creature, change this creature's base power and toughness to that creature's power and toughness until end of turn.

Magda, Brazen Outlaw

Other Dwarves you control get +1/+0.
Whenever a Dwarf you control becomes tapped, create a Treasure token.
Sacrifice five Treasures: Search your library for an artifact or Dragon card, put that card onto the battlefield, then shuffle.

Shapesharer

Changeling (This card is every creature type.)
{2}{U}: Target Shapeshifter becomes a copy of target creature until your next turn.

Renegade Doppelganger

Whenever another creature you control enters, you may have this creature become a copy of that creature until end of turn. (If it does, it loses this ability for the rest of the turn.)

Fire-Belly Changeling

Changeling (This card is every creature type.)
{R}: This creature gets +1/+0 until end of turn. Activate no more than twice each turn.