A week after Ashley Tisdale cosigned that wacky Sharpay Evans fan theory, she tugged on our High School Musical heartstrings all over again.

During her YouTube music session Tuesday (May 23), the Disney Channel alum welcomed a very special guest from her past: Lucas Grabeel, a.k.a. HSM's Ryan Evans.

In the first film, siblings Sharpay and Ryan sing two duets: "Bop to the Top" and "What I've Been Looking For." Tisdale and Grabeel performed the latter on YouTube, but instead of doing it fast and upbeat, they made like Troy and Gabriella and slowed things down.

Turns out, Grabeel wrote the new rendition of the popular song and shared it with his fellow East High Wildcats via text. "It's so good," Tisdale gushed. "He's very talented." The duo haven't sung this song for 10 years, but their performance makes it seem like no time has passed.