Tower

Perry had never been so nervous, when watching his boys use their invention. Phineas and Ferb had build a tower that was filled with traps and obstacles. As Perry sat in his lair, fast-forwarding the security footage, Phineas's words played in his head: 'We'll see you all in fifteen minutes. Or, not at all.' When his boys had finally escaped, Perry released a breath he hadn't realized he'd been holding. They were alright. Thank goodness.

Perry briefly wondered if Heinz got nervous when Perry was trapped.