Callie (Maia Mitchell) and Brandon (David Lambert) took off for Mexico in episode 5 of "The Fosters" Season 3, but the whole family would be together in episode 6 to celebrate Callie's 17th birthday. Unfortunately, the celebration would take a turn when some drama reached a breaking point in the middle of the party. How would it all go down in "It's My Party?"

The episode begins with a big family dinner and Callie (Maia Mitchell) asks Stef (Teri Polo) and Lena (Sherri Saum) if she can buy a car. She has $800 saved and has done an admirable bit of research, but her moms still say no.

Meanwhile, Mariana (Cierra Ramirez) is debating whether she should tell Callie about Wyatt (Alex Saxon). Feeling guilty, on Callie's birthday morning she gives her foster sister $600 so she can get a car safe enough for their moms to approve. However, Callie says she can not accept that much money and instead suggests they buy a car together -- without telling Stef and Lena.

However, their plans are interrupted by Callie's surprise party -- courtesy of Jude (Hayden Byerly), trying to give Callie her first happy birthday in awhile. The party starts off well as Rita Hendricks (guest star Rosie O'Donnell) makes a surprise appearance and Callie's friends perform an impromptu musical number as a tribute.

However, trouble is brewing. Mariana is shocked to see Wyatt has stopped by to celebrate. When he finds out she is newly single, he makes a move on her. She believes if she can get Callie to approve of her and Wyatt, then she would not need to tell her about their past hook up. Later that night, after agreeing to by a car behind their moms' backs, Mariana tests the waters and asks Callie's permission. Callie says yes, but does not seem too happy about it. Mariana does not seem to care, going to talk to Wyatt almost immediately.

Plus, after Brandon overhears A.J. making a mysterious phone call, he gets even more suspicious about his new foster brother. Sophia (Bailie Madison), who is bitter about her parents' divorce and upset Callie's and her father is there, stokes the flames by encouraging Brandon to steal A.J.'s phone to prove to his father (Danny Nucci) that A.J. had been talking to his brother behind Mike's back. When A.J. finds out that Brandon has his phone, the two get into a shoving match in the middle of the party that ends with Mike telling Brandon to leave A.J. alone.

After Stef tells Mike he cannot earn A.J.'s trust at the expense of Brandon, Mike goes to apologize to his son. Then, he goes to A.J., who admits he had been talking to his brother. Mike tells A.J. he cannot stop him from running, but is glad he is talking to Ty and wants him to be happy.

Meanwhile, Lena pulls Mariana aside and tells her Callie is actually hurt she would pursue a relationship with Wyatt. Mariana decides to break things off with Wyatt, but then Wyatt angrily tells Callie everything. She is devastated and confronts Mariana before storming out of the party. Luckily, Robert tracks her down with a birthday present for his daughter -- a car! However, Callie does not accept, wanting to honor her agreement to buy a car with Mariana. After their talk, Robert tries to make things right with Sophia, who is more open to reconciliation after a conversation with Stef.

A happier Callie gets yet another surprise when Jude reveals a moon bounce in the backyard. After everybody leaves, only Callie and A.J. are left on the moon bounce and the pair share an intimate kiss. Unfortunately, Stef saw the whole thing! That is sure to cause some drama in the next episode.