- “So you call that a little game?”
- — Chad to Ryan; High School Musical 2
High School Musical 2
Chad and Ryan don't interact at all in the first movie, but have multiple moments together in the second movie. There's tension between them at the start of the number "I Don't Dance", but are getting along by the end.
After the game Chad and Ryan are eating, and wearing each other's outfits, when Chad asks Ryan about how good he got at baseball. Ryan tells him that he played in the little league champions, Chad rolling his eyes. Ryan reveals that his team were the champions, and Chad looks at him in shock, before playfully shoving him.
Shipping tends to happen when those who had watch the films as a child re-watch them again and noticed chemistry between the two during "I Don't Dance". Ryan being coded gay also adds fuel for the shippers.
Tumblr user batmanisagatewaydrug wrote an entire plot summery for a possible High School Musical 4, that would take place during Chad and Ryan's wedding. The post currently has almost 175,000 notes. Several other social media users have also made posts discussing the chemistry between Chad and Ryan.
Chad also wears a shirt in High School Musical 2 with the text "He did it." written on it in capital letters. Some see this as Chad celebrating Troy and Gabriella's kiss. However, due to the fact that Chad is seen wearing it after Ryan's talent show, Chyan fans see it as Chad celebrating Ryan winning the talent show. 
On AO3, Chyan is the most written ship for both Chad and Ryan. It's also the most written ship in the High School Musical tag.