It's amazing to me that despite having not seen an episode (or clip) of the show in years, on reading your comment I was still able to immediately hear that unm

It's amazing to me that despite having not seen an episode (or clip) of the show in years, on reading your comment I was still able to immediately hear that unmistakable "bubbling" engine sound in my head. Good luck in your search - that will be a fun effect to play with :)