Transforming Flourish

Demonstrate (When you cast this spell, you may copy it. If you do, choose an opponent to also copy it. Players may choose new targets for their copies.)
Destroy target artifact or creature you don't control. If that permanent is destroyed this way, its controller exiles cards from the top of their library until they exile a nonland card, then they may cast that card without paying its mana cost.

Bulk Up

Double target creature's power until end of turn.
Flashback {4}{R}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Creative Technique

Demonstrate (When you cast this spell, you may copy it. If you do, choose an opponent to also copy it.)
Shuffle your library, then reveal cards from the top of it until you reveal a nonland card. Exile that card and put the rest on the bottom of your library in a random order. You may cast the exiled card without paying its mana cost.

The Twelfth Doctor

The first spell you cast from anywhere other than your hand each turn has demonstrate. (When you cast that spell, you may copy it. If you do, choose an opponent to also copy it. A copy of a permanent spell becomes a token.)
Whenever you copy a spell, put a +1/+1 counter on The Twelfth Doctor.

Replication Technique

Demonstrate (When you cast this spell, you may copy it. If you do, choose an opponent to also copy it. Players may choose new targets for their copies.)
Create a token that's a copy of target permanent you control.

Bill Potts

Whenever you cast an instant or sorcery spell that targets only Bill Potts or activate an ability that targets only Bill Potts, copy that spell or ability. You may choose new targets for the copy. This ability triggers only once each turn.
Doctor's companion (You can have two commanders if the other is the Doctor.)