Do children and adults engage in spontaneous Theory of Mind (ToM)? Accumulating evidence from anticipatory looking (AL) studies suggests that they do. But a growing body of studies failed to replicate these original findings. This paper presents the first step of a large-scale multi-lab collaboration dedicated to testing the robustness of spontaneous ToM measures. It examines whether 18-27-month-olds and adults’ anticipatory looks distinguish between knowledgeable and ignorant agents. In a pre-registered study with toddlers [anticipated N = 440, 50% female] and adults [anticipated N = 360, 50% female] from diverse ethnic backgrounds, we found that [DESCRIBE RESULT AND EFFECT SIZE FOR MAIN CONFIRMATORY ANALYSIS]. This provides [SUPPORT/SOME SUPPORT/NO SUPPORT] for spontaneous, epistemic state-based action anticipation in an AL paradigm.