Cast Oko by paying ({2} magic symbol) ({G} magic symbol) ({U} magic symbol) , causing it to enter the battlefield with six loyalty counters due to Doubling Season.
Cast Spark Double by paying ({3} magic symbol) ({U} magic symbol) , choosing to have it enter the battlefield as a nonlegendary copy of Oko, and to enter the battlefield with eight loyalty counters due to Doubling Season.
Activate an Oko's third loyalty ability by removing five loyalty counters from it, causing you to create two token copies of each other nonland permanent you control.
If you created any legenedary tokens this way, put all but one of them into your graveyard due to the legend rule.
Repeat from step 3 using a different Oko.
Once you have infinite Oko tokens, you may instead activate Oko's other abilities.
Results
Infinite copies of nonland permanents you control.