Railway Brawler and Temur Sabertooth on the battlefield.
({4} magic symbol) available in at least three different colors available.
Steps
Cast Crystalline Crawler by paying ({4} magic symbol) , ensuring to spend at least three different colors of mana to cast it, causing Crystalline Crawler to enter the battlefield with at least three +1/+1 counters on it.
When Crystalline Crawler enters the battlefield, Railway Brawler triggers, putting four +1/+1 counters on it.
Activate Crystalline Crawler's first ability by removing all +1/+1 counters from it, adding ({G} magic symbol) ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) and the remaining mana in any combination of color(s).
Activate Temur Sabertooth by paying ({1} magic symbol) ({G} magic symbol) , returning Crystalline Crawler to your hand from the battlefield.