This show is legendary for many reasons. Liza Minnelli did not want to do it, but once MAMA announced ticket sales before informing (asking) her on-the-rise daughter, Liza was stuck with this gig.
Liza got her revenge by wiping the floor with MAMA in the first act.
Rest assured, JUDY GARLAND returns with a vengeance in the second act. For me, this segment has always fascinated me on many levels. Many.
All of this is not available on DVD. I have the CD, you can probably get it. There is a very truncated VHS on EBay (or elsewhere: I saw it and I don't recommend, even if you're a fan--it's a TV show version and is not very well done). You are better off with the 2-DISC CD. It's classically reproduced.