For the main WMG for Trolls, click here.
The Party Crashers were sent by the Rock Trolls to scout Pop Village for weaknesses and capture their String
Why do the Party Crashers listen to Rock music and have Punk Rock-style clothing? It's because they hail from Volcano Rock City and were hired by the Rock Trolls when Barb learned of their existence. She told Bash to search Pop Village for the Pop String and he'll get all the party supplies he wants.