Bill and Dipper
The puppet show was one of the most difficult tests of trust the twins had to endure, where their bond grew even stronger, and together they managed to defeat Bill Cipher for the second time before it was too late.
but...
What would have happened if it hadn't ended this way?
What if Mabel had hesitated to give the journal to Bill?
What if that bond was broken?
What would have happened... if Dipper had trusted Bill?
"There were only two people inside that body who called themselves Bipper"
"Bill and Dipper"