The TMZ Celebrity Tour Bus hit the streets again Wednesday night — and this week’s surprise guest was none other than Diplo!

Yep, the superstar DJ pulled up for the Hollywood tour alongside British babe America Foster … who opened up about making history as the first female member of EDM group Major Lazer.

The vibes were already turned all the way up — because it also happened to be Foster’s birthday … the singer celebrated hard onboard, dancing it up and flexing some seriously killer vocals for the crowd.

The whole thing turned into an absolute party on wheels … and Diplo even dropped a wild comment about Judge Judy that totally caught everyone off guard!