Oh yes, now when you mentioned it, there is that scene too.
But the scene I am talking about is when Michael is adult, after he escaped from the asylum and when he start killing again at the halloween, in the "final stage" of the movie.
It is Laurie, his sister who was baby when he killed his step-father, older sister and her boyfriend, she was adopted by the Strode family.
She stays at home babysitting two kids (a boy and a girl - I think that the girl is younger sister of one of her friends, can't remember though). Lauren is lying on the couch and kids were talking about some boogeyman or something like that, when she tells them to stop talking about it, then they say that she is scared and start a tickle attack. She says something like "leave me alone for five seconds", then they stop and start counting toghether 5, 4, 3... Then she says "okay, okay, don't", while laughing, meaning not to tickle attack her again and then they start tickling her once again. She say something like "I'll tell you to your parents" and then the scene is over.
Here's the picture of the girl who played her, she wears glasses in the movie: