The kids decide to make a giant bookshelf for Lawrence, but they eventually have to defend it from an army of anthropomorphic plants that were created by/look like Doofenshmirtz in hopes of taking over the Tri-State Area. Meanwhile, Candace tries to bust the boys by using psychological methods on Linda.
Plot[]
In the backyard, Buford is once more attempting to win over the rest of the gang with his Bread Bowl Hot Tub. Phineas is about to approve it, when he hears his father having an accident in the garage. As the gang approach him, they see that his favorite bookshelf has finally given out. Phineas decides that instead of the Bread Bowl Hot Tub, they will make the ultimate bookcase for Dad.
Perry enters his lair via a giant pinball machine, ultimately overtaking Carl's high score. Major Monogram informs Agent P that there has been an abundance of plant life on Doofenshmirtz's balcony.
Back in the backyard, Lawrence goes back to the garage to get his wrench, but then forgets what he was looking for and goes through all the junk in the garage. Buford is initially hesitant to join the project, since he believes that reading is boring and the bookcase is not a Bread Bowl Hot Tub. But when the gang decide to add some amenities, including the possibility of a soupy loaf jacuzzi, Buford rejoins them. As the gang gathers books to put on the shelf, Candace finds a book on hypnotism and attempts to hypnotize her mother to get her to bust the boys, but Linda is not fooled, since she also believes the bookcase the boys are building is nothing bustworthy.
At Doofenshmirtz Evil Incorporated, Perry gets trapped in a giant wad of chewing gum. Doof has taken up gardening, since back in Gimmelshtump, during his days as a lawn gnome, the local kids would, for some reason, bully him for not practicing photosynthesis, even though that is only exclusive to plants. So he made the Face-Plant-inator, which would grow omnivorous plants that have his face. As Perry frees himself from his trap, the Doofenplants grow wild and out-of-control.
After Phineas and the gang complete their bookcase, they realize that Dad is still missing. Meanwhile, Candace attempts using reverse psychology on her mother to get her to come outside, but Linda fights back using a triple negative on her. Phineas and the gang find Lawrence back in the garage, still rummaging through his antiques, when they show him the bookcase. He is very impressed by the shelf as well as the collection of books. He goes back in the house to get his wife to show her.
Back at D.E.I., Doof and Perry are still under attack from the Doofenplants. They attempt to get to the self-destruct button, but the plants block their path. Perry fights Doof and causes him to fly backwards and hit the inator.
The inator's beams hit the backyard, causing Doofenplants to grow all over and start eating the bookcase. The gang get out books on getting rid of weeds... and hit them with the books. They also get out swords to attempt to prune them, but they are largely outnumbered. In the house, Candace resorts to begging and bargaining to get her Mom to the backyard. But then, Lawrence politely requests her to come out, and she accepts.
Back at Doof's lab, Perry finally reaches the inator's self-destruct button, causing the plants to explode. As the inator also undergoes its own inevitable explosion, Doof curses Perry and his own hubris. When he lands in soil, he is suddenly confronted by the now-grown Drusselsteinian bullies, who still make fun of him for not practicing photosynthesis.
In the backyard, the Doofenplants all explode, and the bookcase is now reduced to a much smaller case. Linda is impressed, Candace is confused, and Lawrence is just as perplexed since it "seemed bigger". As he finally finds his wrench, the gang jump in the air and freeze in celebration doing a "Yeah! shot". Perry returns, and Candace comes upon the still-frozen gang, calling them "so weird".
