I don't believe Matilda has any exceptional quick quick changes for the leads. One I can think of is a male ensemble member who plays a dad during Miracle also plays Rudolpho in the same scene. I also imagine the Acrobat, Escape Artist, and Michael have some quick changes too (going from school kid to the acrobat/escape/Michael W costumes. After Revolting Children, I think three ensemble members play Russian Mafia. So that would probably be very quick too.
I'm not sure if you would know, but am i right to think the couples in opening number also play older children and the dancers in the competition? they surly dont have other roles too?
its just company/ensemble who dont play parents in opening number then play mafia/circus people?
If I'm understanding your question correctly. The adult Ensemble in Matilda plays Parents in MIracle, School Children, Loud dancer/Judges and each of them have their own smaller part. For example, the ensemble member who plays the Escape Artist also plays a parent in Miracle, a school child, and judge. The woman who plays the Cook also plays a loud dancer, a schoolgirl, and parent. There are 10 adult ensemble members on stage (not including swings.)