In Props, the twentieth episode of Season Three, Tina bumps her head and the New Directions swap bodies in Tina's dream.
Accident

      Tina falls into a fountain while she is text fighting with Mike on her phone and carrying different fabrics for costumes. Blaine and Kurt try to help her.

Finn - Kurt
       During Tina's dream, Finn becomes Kurt. Finn and Puck as Kurt and Blaine come to help Tina as Rachel out of the fountain. At school, Finn (as Kurt) asks Tina to go to Between The Sheets, but Puck (as Blaine) starts arguing with him about Chandler. During Tina's solo, they are cuddling together.
Kurt (as Finn) was seen later in the choir room sitting next to Tina (as Rachel) when everyone wants her to show what she has prepared for Nationals. She says no, then Kurt (as Finn) says he needs to speak to his fiancee. They get up together, then Kurt (as Finn) tells her that she's not acting herself and encourages her to work her best, and how he can't wait to make out with her after school because her boobs look strangely bigger today.

Puck - Blaine
    During Tina's dream, Puck becomes Blaine. Finn and Puck as Kurt and Blaine come to help Tina as Rachel out of the fountain. At school, Finn asks Tina to go to Between The Sheets, but Puck starts arguing with him about Chandler. During Tina's solo, they are cuddling together.
During Tina's dream, Blaine becomes Puck. He is seen yawning during Tina's performance.

Tina - Rachel
      During Tina's dream, Tina becomes Rachel. At first, since this is her dream, she is perplexed and confused as to why Blaine and Kurt look like Puck and Finn, respectively, and why they call her "Rachel," but then she looks down to see her wardrobe has changed. She begins to catch on and act more like Rachel after singing Because You Loved Me.
    During Tina's dream, Rachel becomes Tina. Interestingly, she appears as a season one Goth Tina. At the end of the dream, "Rachel" tells "Tina" that she appreciates her support. In return, "Tina" tells "Rachel" some advice about how to approach Carmen Tibideaux. Later in reality, the real Tina gives the real Rachel the same advice.

Santana - Artie
       During Tina's dream, Santana becomes Artie. While she is Artie, she tells Tina as Rachel that she needs to do good as it could mean a lot to disabled kids everywhere. She also does Artie's signature "Preach" hand gesture during Tina's performance.
During Tina's dream, Artie becomes Santana. Although Santana is now on good terms with Rachel, Artie as Santana is mean to Tina as Rachel. During Tina/Rachel's solo Artie/Santana sits with Mercedes/Brittany and they share a brief kiss.

Mike - Joe
       During Tina's dream, Mike becomes Joe. He is seen watching Tina's solo with the rest of New Directions, and pushing his dreads back out of his face once Tina's solo ends.
       During Tina's dream, Joe becomes Mike. He is seen sitting next to Rachel as Tina during Tina's solo as Rachel. He randomly dances in his seat during the performance. When Tina finishes her solo, he randomly dances then as well.

Quinn - Sugar
      During Tina's dream, Quinn becomes Sugar. She is seen being very over-excited and is jamming out to Tina's solo.
      During Tina's dream, Sugar becomes Quinn. She is seen listening to Tina's solo.

Sam - Rory
         During Tina's dream, Sam becomes Rory. He is seen with his arm around Sugar during Tina's solo.
During Tina's dream, Rory becomes Sam. He is seen looking very bored during Tina's solo.

Mercedes - Brittany
       During Tina's dream, Mercedes becomes Brittany. She talks to Tina as Rachel saying that she needs to bail Lord Tubbington out of jail for selling her iPod for drugs.
       During Tina's dream, Brittany becomes Mercedes. She is seen wheeling Santana as Artie around and says "Praise."

Will - Sue
       During Tina's dream, Will becomes Sue. He tells Tina as Rachel to hurry up, and when Sue as Will tells him that it is racist, he says that he is part Cherokee. He is then is seen covering his ears during Tina's solo.
        During Tina's dream, Sue becomes Will. She tells Will as Sue to not be racist and asks Tina as Rachel to sing her solo.