Enchant creature
When Wolfkin Bond enters the battlefield, create a 2/2 green Wolf creature token.
Enchanted creature gets +2/+2.
If the target creature is an illegal target by the time Wolfkin Bond tries to resolve, the spell doesn’t resolve. It won’t enter the battlefield, so its ability won’t trigger.
You need a creature for Wolfkin Bond to target as you cast it. It can’t enter the battlefield attached to the Wolf token it will create.