If you want to reply "I can see that catering is not for nothing" in a humorous way, you can consider the following ways:

1. Tease the other person: You can say, "Haha, you have been in the catering industry for so long, and now you just find out!" Or "I always thought you were a chef, so you were a manager in the catering industry!" "

2. Laugh at yourself: You can say, "Yes, I worked so hard in the catering industry, and you saw it, but I didn't." Or "I always thought my job was cooking, but I found out that I was actually a waiter!" "

3. Humor summary: You can say, "Haha, I can see that there is no free dining, but I have worked so hard, but you have seen it so easily!" Or "Yes, I have worked so hard in the catering industry that you can see everything after just looking at it!"

no matter which way you choose, you should pay attention to maintaining a friendly and respectful attitude.