Place pork, Teriyaki sauce, rice vinegar, garlic, and red pepper flakes in slow cooker.
Cook on low for 6-8 hours.
Remove meat from the slow cooker and shred.
Stir peanut butter into the remaining liquid.
Add sliced peppers, and return meat to slow cooker.
Cook approximately 30 minutes until peppers are slightly cooked, but still crisp.
Just before serving, stir in green onion and cilantro.