I'm going to throw this out there but I'm not sure if it's what you are referring to as your question refers to Lesson 3; Bubbles 1 and 2.
When we began entering code, I had a student who would copy the code on the actual Code.org web page and paste it into his lesson. It appeared as though he was completing the work. After our discussion, I let the student know I was aware of what he was doing. Since he felt he "already knew" HTML, I asked him to be the Lead Student Coder and to work through each of the lessons at his own pace. Needles to say, I kept an eye on him! He was a great help when a student needed some assistance with a particular lesson-- since he had already completed it.