About a year and a half ago, Laura Henderson, a toy company executive and 38-year-old mother in Toronto, was at the tail end of maternity leave with her second child. She was bleary-eyed and overwhelmed, as mothers juggling an infant and toddler tend to be, when she started scrolling TikTok and stumbled upon the children¡¯s personality known as Ms. Rachel.

That name probably means nothing to you ¡ª unless you regularly spend time with a child under the age of 3, in which case you¡¯re likely aware that she is essentially Taylor Swift for toddlers. Ms. Rachel is the star of a mega-viral YouTube channel created with her husband (known to viewers as ¡°Mr. Aron¡±) who makes educational musical videos for the baby and toddler set, complete with bursts of animation and Broadway-worthy show tunes.

In the videos, dozens of which each top 100 million views, Ms. Rachel, whose real name is Rachel Accurso, cheerfully speaks to young viewers while wearing a signature outfit of denim overalls, a pink T-shirt and a knotted pink headband. Little ones go wild for her version of ¡°Hop Little Bunnies¡± and for characters like a fluffy orange puppet named Herbie, voiced by her husband, Aron Accurso. She does a lot of peekaboo and dramatic wondering of ¡°what¡¯s in¡± boxes: ¡°What¡¯s in the box? What could it be? Will you take a look inside the box with me?¡±