If I had done something to change my appearance I would tell them what it was. If I hadn't I would say 'No, it's the same old me!'

Even if you are the same, it is best to go with it. Say; "what do you think is different?". If they say anything, right or wrong, answer - "Yes. You got it! You are more perseptive than people give you credit for." If they can not answer; say - "I will let you think it over. Just noticing shows me you are a very perseptive and intuitive person."

I'm Just the same as normal. Or I'm just the same as I normally am .

ahem... in my perspective, if somebody says that you are different. you should bring positivity into the mood. you ought to think that you are different in a good way. don't put "it's the regular me" in your dictionary entries, bad idea. so, somebody says to you, "You look different today." "Thank you. You notice that. I feel better than the yesterday's me. Feel so energized and ready to shake the world. Just see me rolling and i could be your inspiration." That's the kind of response that will blow everybody's mind and bring fresh air into the room ;) your next homework is to walk the talk. if you think you are more awesome than yesterday, appreciate your life more by doing things that make you feel to be living the life to the fullest.

If someone thinks you look different, you might ask yourself "what makes me look different?" They are trying to be honest, or just speaking their mind. Maybe you gained or lost some weight. You might ask them "what looks different? I feel the same." It's not a bad thing; just a comment. Just say, "Oh, I do? It's just me" like you said. That is fine.