I think they had a contract with the same preschool band to do any episode involving sea devils. I love your description - right up there with the observation I read elsewhere that partway through Silurians the kazoo player apparently accidentally inhales his kazoo and tries to keep valiantly playing anyway. The random bonks of wood-blocks and triangles sure sounds like preschoolers to me...

One of my dreams is for someone to please, please re-score those two eps, the acting and plots are really pretty good in both but the music is painful.

*goes back to see T-shirt!Doc again and feels better*