When Linda and Candace are pushing the groceries through the store parking lot, you can see the 'future' versions of Candace from the Quantum Boogaloo episode hiding behind one of the cars.
In the original "Rollercoaster" when Candace first checks on the boys, Phineas acted snarky to her and passed the project off as homework. Due to his change in personality since the show was originally in development, in the remake, he says to her, "The condition didn't have to do with the moose, did it?"
Buford breaks the fourth wall when he takes the poster away from the three boys and says he's not going to be seen with "you lousy extras". Sure enough, Buford, Baljeet, and the Fireside Girls replace the original passengers in the rollercoaster.
Much of the scenes are recycled from the original "Rollercoaster". It's most noticeable during the rollercoaster scenes as the original boys can be seen instead of Buford, Baljeet, and the Fireside Girls.
Baljeet and Millie's voice actors are credited only for their screams during Phineas's song on the rollercoaster.