Agent Frank Horrigan enters the battlefield, it triggers, causing you to put two +1/+1 counters on
Cryptic Trilobite.
Activate Crystalline Crawler's first ability twice by removing two +1/+1 counters from it, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) that can only be spent to activate abilities.
Repeat.
Results
Infinite +1/+1 counters on
Cryptic Trilobite.
Infinite blinking.
Infinite colorless mana that can only be spent to activate abilities.