The Sixth Doctor, Romana II, and Gideon, Martial Paragon

Prerequisites

• The Sixth Doctor on the battlefield
• Romana II on the battlefield
• Gideon, Martial Paragon on the battlefield
• undefined available

Steps

1. Cast Gideon by paying
2. The Sixth Doctor triggers, copying the Gideon spell, with the copy being nonlegendary
3. Resolve both Gideon spells
4. Activate a mana-producing creature by tapping it, adding at least
5. Activate Romana II by paying and tapping it, creating a copy of the Gideon token
6. Activate a Gideon token's first loyalty ability by putting a loyalty counter on it, untapping all creatures you control and giving them +1/+1 until end of turn
7. Repeat from step 4

Results

• Infinite untap of creatures you control
• Infinite mana creatures you control can produce
• Infinitely large creatures until end of turn