Lawrence's memory is accidentally erased by a gadget in Perry's lair before participating in a father-daughter race with Candace, so Perry operates a robot version of Lawrence to fill in for him. Meanwhile, Dr. Doofenshmirtz invents an opposite of glue named "Eulg," which breaks stuff apart rather than join it together.
Candace and Suzy try to get Phineas and Ferb to bust themselves, the boys build a replica of Niagara Falls so they can ride a barrel over it, Doofenshmirtz builds a device to increase his carbon footprint.