Progenitor Mimic

You may have Progenitor Mimic enter the battlefield as a copy of any creature on the battlefield, except it has "At the beginning of your upkeep, if this creature isn't a token, create a token that's a copy of this creature."

Nexos

Strategic Coordinator — Basic lands you control have "{T}: Add {C}{C}. Spend this mana only on costs that contain {X}."

Unbound Flourishing

Whenever you cast a permanent spell with a mana cost that contains {X}, double the value of X.
Whenever you cast an instant or sorcery spell or activate an ability, if that spell's mana cost or that ability's activation cost contains {X}, copy that spell or ability. You may choose new targets for the copy.

Venomthrope

Spawnwrithe

Trample
Whenever Spawnwrithe deals combat damage to a player, create a token that's a copy of Spawnwrithe.

Biowaste Blob

Oozes you control get +1/+1.
At the beginning of your upkeep, if you control a commander, create a token that's a copy of Biowaste Blob.

It Came from Planet Glurg

You may have It Came from Planet Glurg enter the battlefield as a copy of X different creatures on the battlefield. (It has their total power, total toughness, combined mana costs, all text boxes, names, art, and so on.)