Confidence:StrongSolidPlausibleTentativeSpeculative

• Oko, Lorwyn Liege // Oko, Shadowmoor Scion

  2U

  Legendary Planeswalker — Oko // Legendary Planeswalker — OkoGU

  Both cards produce the same kind of effect (shared token subtype).
• Watchful Radstag

  2G

  Creature — Elk MutantG

  Both cards produce the same kind of effect (shared token subtype).
• Mirror Room // Fractured Realm

  2U5UU

  Enchantment — Room // Enchantment — RoomU

  Mirror Room makes Oko, the Ringleader's triggered ability trigger an additional time — each time it fires, you get it twice. Value, not a loop.
• Rings of Brighthearth

  3

  ArtifactC

  Oko, the Ringleader has activated abilities that aren't mana abilities, fueling Rings of Brighthearth's activation-trigger.