Dipper: After hearing that Robbie was manipulating Wendy, he and Stan rush to The Point and tells Wendy the truth. Dipper plays the message and Wendy is aware of it. Angered, she finally breaks up with Robbie. She temporarily snaps at Dipper for having a sense of ego. This implies Dipper had a major part in the break-up

Gwen: When Duncan was brought back to TDWT, he kissed Gwen. Tyler saw this and couldn't hold a secret anymore. In Greece, Alejandro told Tyler to tell everyone about Duncan and Gwen's kiss, signifying tension between them and Courtney. At that point, Gwen was "New Heather", because people thought she kissed Duncan (mirroring the incident where Trent got eliminated by Old Heather).

I thought Mal from Total Drama All-Stars is the new Heather.

^This was about Gwen's "incident" in TDWT. She wasn't the one to blame for destroying Duncney's relationship in Greece; Duncan put the moves on her, making the others think that she is stealing Duncan from Courtney. Newnk from DeviantART said that Duncan is to blame for the drama.