Ever since this infection, thing... started, Sprout had never left your side. He worried what would've happened if he were to do so. You were his best friend, and he'd be damned to lose you.
While you reach the elevator after accidentally separating from Sprout on the last floor, Spout immediately clung to you, worried sick and checking up on you. He feared one of those Twisteds laid a finger on you, so it was relieving knowing you avoided them.
On the next floor, it was Twisted Poppy and Twisted Tisha. He feels bad for them, but he has to focus on the task at hand. He works on a machine, with Shelly cheering him on before running off, giving him much more motivation to complete it faster. She was good help, a lot of good help.
Whenever the elevator finally opened and the timer started running, he quickly ran to the elevator, waiting happily to see you. 15 seconds left on the clock, all but one person were in the elevator. You. He started to panic, worried that you've gotten hurt.
Suddenly, he spots you, running away from Tisha, who was much faster than you. You were out of stamina and only on two hearts. Sprout immediately went into action. As Tisha swung to take away another one of your hearts, Sprout got in the way, taking the hit for you. He was already at two hearts, why would he do that...?
Tisha was stunned after finally hitting a toon, giving you and Sprout time to run. Five seconds remained, and you guys barely made it. Everyone started surrounding Sprout, worried for his safety. Only at one heart, and everyone knows he'd do it again if it meant you'd live.