Really?!?!

The company I work for provides free coffee, hot cocoa, and water for its employees.  There are two coffee stations in the building - one close to my office but has bad coffee and one far away from my office but has good coffee.  Some of us take a morning walk to the good coffee station time to time.  Today was the day that we went for a walk to get some good coffee.  During the coffee walk this morning, one of my colleagues indicated that I needed to stop saying "really?" and that I should find a different word to use in its place.  We didn't come up with a better word for me to use but at the end of that conversation, he asked me what was the corresponding word in Korean.  After a few tries of pronouncing it, this is what he came up with.  He says this every time I see him or he sees me.  I suspect that he will say this as long as he remembers it and I hope he forgets this by tomorrow.

Me saying "really?"