Feeling bad about missing his actual birthday party, Yin and Yang pretend to be Dave's students at his post-birthday party. Will the power of friendship keep the lie together, or will Dave be found out?
Yin and Yang are trying to have a fight with Carl the Evil Cockroach Wizard, but Coop keeps popping up and interrupting it. He keeps asking whether or not Yin and Yang are good friends with Dave. When they finally tire of Coop's questions and say that they are Dave's friends, Coop then asks them why they missed Dave's birthday party. When Carl hears this, he thinks it will be much more interesting and potentially more destructive for Yin and Yang to face Dave's anger than against one of his own plans. So Carl stops attacking and lets Yin and Yang go, since Carl didn't have any good plans today anyways.
When Yin and Yang arrive in the forest where Dave lives, the party has long since been over. Dave dejectedly says that it's okay because he figures that he's just not important or good enough as a friend for Yin and Yang to bother remembering about Dave's birthday party. Yin and Yang of course, feel pretty bad about this, and say to Dave that whatever they have to do to prove their friendship to Dave, they will do it! Then Dave gets a phone call from his parents. His parents have decided to throw Dave a Day-After-Birthday Party, and Dave is inviting his friends, Yin and Yang! Unfortunately, going to a party where a bunch of trees will be is the Last thing Yin and Yang want to do with their spare time, but they already made a promise to Dave, and they don't want to back out now and be seen as liars.
So the day of the party comes, and a lot of the trees aren't as lifeless as Yin and Yang thought they would be. They end up meeting a lot of Dave's family tree (no pun intended!) at this party where Dave introduces his friends, Yin and Yang, as his Woo Foo Students! Yang is about to expose the truth to Dave's family by threatening to get an ax, until Yin realizes that an intervention is necesary. They go into a restroom, and Yin tells Yang that Dave is their friend and they should be helping them by remembering Master Yo's lesson. And Master Yo's image appears in the water of the toilet saying that no good ever comes of lying to a friend, but the truth will always save the ones you care for in the end. But Yin is confused because their lying is actually helping Dave become cooler with his parents, and now they don't even know what Master Yo's lesson is supposed to be about. So Master Yo's image gives up and tells Yin and Yang to figure it out! Yin and Yang decide to play along with Dave's claim for a while. Yin helps out by magically levitating Dave, Yang helps out by cutting up Dave's sandwiches for him, and Yin and Yang prove their fire resistance to Dave.
Yin and Yang call for a time out first, and run back into the restroom! Yin and Yang know there must be some point to the lesson Master Yo is trying to teach them, if they could only figure out what it is. Then Master Yo's image appears to remind them about the lesson again. Then Yin figures it out! It's not the lying of the Woo Foo Warriors that is causing all of this trouble, it's Dave! So they tell Dave that they will not play along with his game anymore and that Dave can handle his problem himself! But Dave knows that he actually can't handle the problem himself! Chip is a level 20 Wedgie Master and Dave can't compete with that!
Unfortunately, Dave has something much graver to be worried about. Carl is camping in the woods and has finally come up with another plan. Out of spite and pure evilness, Carl decides to burn the forest to the ground with Fire Spirits! And while some of Dave's family can move and run away, some are actual trees and are stuck in the ground. Yin and Yang know that they have to save them. So Yang sucks up the bad guys with the Reverse Foo-nado, while Yin douses out their flames with a giant pitcher of lemonade, and as extra insurance, they seal up the doused flames inside a cup used for the lemonade with a talking acorn who threatens to open them up if someone makes a joke about roasted chestnuts. When Dave sees how his friends saved him even after his lying, Dave decides to tell the truth and confesses that he's not a Woo Foo Master at all. Dave only said that stuff to impress his family so that they would think he was cool. And Yin and Yang aren't his students, they are his friends.
Dave's parents are actually (and surprisingly) relieved because they thought that their son was practicing Woo Foo for they feel it's stupid; even so, Dave's mother giggles and states, "I rather have a son who lived in the gutter and ate filth." Yin and Yang feel shocked at their ungratefulness because Chip told them that Dave tricked the rabbits into doing the dirty work for them and he admits that Dave is not a total dweeb after all. Right after that, Yin (and/or Yang) set the forest back on fire as Dave frantically screams for help while Yang stands by a rock and thinks he should put it back out again in five minutes which works for Yin who is proud of him for not saying nuts.
- This episode features Carl as the main antagonist