United Kingdom, June 4 -- Ashley Tisdale refuses to do more than "two-hour sessions" for 'Phineas and Ferb'.

The 39-year-old actress - who has voiced Phineas' sister Candance since the pilot episode in 2007 - is back for the beloved animated comedy show's revival a decade after the 'Last Day of Summer' finale aired, and she has reflected on the challenges of recording the voiceovers.

She told PEOPLE magazine: "That's always been kind of more of my challenge with Candace, is when she starts to kind of build into that episode and she's really high-strung, and it takes a lot out of me.

"So, I only do two-hour sessions. But I've been doing only two-hour sessions from the very beginning.

"I recognised very soon into Candace that I was like...