Activate Marvin using Cradle Clearcutter's ability by tapping it, adding at least {G}{G}.
Activate Marvin using Pili-Pala's ability by paying {2} and untapping it, adding one mana of any color.
Repeat.

Infinite colored mana

Marvin, Murderous Mimic

Pili-Pala

Cradle Clearcutter

Activate Marvin using Cradle Clearcutter's ability by tapping it, adding an amount of {G} equal to its power.
Activate Marvin using Farmstead Gleaner's ability by paying {2} and untapping it, putting a +1/+1 counter on Marvin.
Repeat.

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