Guys guys I had a THOUGHT.
Do you think they cast Yelchin as Chekov in part because his hair is curly so they knew they would never ever be stuck with prime Chekov's MONKEES style hair? As in people would either be whining where is my MONKEES hair or they would be whining why do we have this lameass MONKEES hair. And if they did use the MONKEES hair people would whine why don't the women have the 60's do's why is it only Chekov who looks this dated. But since his hair cannot actually go MONKEES because it is curly we will never ever face this.
I'm thinking this was a plan.
Clearly you've never seen Micky Dolenz in the early episodes of the Monkees.