The second time the boys go
through the wormhole, Kenny is seen in the craft with them, even though he is on Sally the Hutt's ship frozen in carbonite.
While Cartman and Sally the Hutt talk, the men at the helm are either Marklar (when the camera is behind them) or something else (when the camera is before them).
Cartman already tried to push the red button to go to Marklar planet but it didn't work but later he says he remembered the button and presses the same red button again and this time it sends spacecraft to planet.