As others have noted in the past, Danny DeVito not only directed Matilda (and played her dad), but he and Rhea Perlman (DeVito’s wife at the time and Matilda’s mum in the movie) basically looked after Mara Wilson because Mara’s mother was in hospital with terminal cancer at the time of filming (She died during post production work, and it wasn’t until years later Mara discovered that Danny had taken an advanced (not quite completed) copy of “Matilda” to the hospital so that her mum could watch it before she passed.)

When Mara mentioned that she was feeling nervous about the dancing to “Little Bitty Pretty One” sequence, it was DeVito’s idea to have the ENTIRE cast and crew join in and dance too (off camera) so she wouldn’t feel self-conscious, apaprently even the craft services folks joined in, and the cameraman shooting the scene did a bit of a shuffle, but not too much because it would mess with the camera shot)