The Three Ds

From Muppet Wiki

The Three Ds are a tutu-clad singing group who appear in the pre-show for Muppet*Vision 3D. Discovered by Fozzie Bear, and deemed ideal for a 3D movie, the group normally consists of Dorothy, Dinah and Debbie. The latter is sick, however, so the union sends Max instead. The trio mangles a portion of "By the Light of the Silvery Moon" before Scooter shoos them out.