What is slappy's weakness?

Slappy, the infamous ventriloquist dummy from R.L. Stine's "Goosebumps" series, is primarily weakened by the power of belief. He is susceptible to being rendered powerless when someone shows determination and confidence in resisting his commands. Additionally, in various stories, Slappy's vulnerability is linked to the presence of the magical incantation that can control or banish him. Ultimately, overcoming fear and asserting one's will can diminish his influence.