I love analyzing my native language, American English, and helping non-native speakers make sense of it. I've been doing this for fun with friends who speak English as a second language for nearly 30 years. I would like to first thank A.D., C.F. and E.A., and now P.G., for inspiring me to finally write this stuff down!
'I know, right?!' is an expression used by Americans to show the other speaker they hear or understand what the other person is saying or means, and agrees with them.
Example:
-Your total is $3.00.
-$3.00 exactly?
-I know, right?!