A kiss
As Dan and Wendy hung out, Dan thought he would buy her some ice cream to celebrate her finishing high school, a small, but cute gesture. As they ate ice cream together, they began to talk about feelings and this is when Dan went in for a kiss. It was a success.
Wendy kissed him back and from there on out, the two were officially dating. No longer were they friends, they had waited a year and it had paid off for them, just like they thought it would. Now they were a couple and the next phase of their relationship was about to begin.