Many tools assess the reactions of humans encountering familiar or unfamiliar partners or environments. Companion animals belong to our everyday environment and influence our lives. Whereas many standardized tools test companion animals' reactions to humans, few evaluate humans' reactions to companion animals. We present here a test with a guinea pig that can be applied to a wide range of people in the home environment. This standardized test and simple coding system enabled us to characterize individual behavioral profiles of children and compare them in relation to different factors (e.g., gender, age, pet ownership). We observed 59 children (32 girls, 27 boys), aged between 6 and 12 years old. Our results show that most children first looked at the guinea pig (72%), smiled when they saw it (49%), and then went directly towards it without looking at their parent (79%). Many children touched the animal without hesitation (86%). Moreover, this test reveals more than the mere interest of children in guinea pigs. Indeed, a cluster analysis differentiated four behavioral profiles that reflected aspects of the children's experience, gender, and lifestyles. When encountering the unfamiliar guinea pig, children could be "confident" (go straight to the animal and touch it; 64%), "anxious" (look at parent; 12%), "indirect" (hesitate and touch; 14%), or "careful" (emit vocal and/or verbal behaviors; 10%). The potential future application of this research is to compare behavioral profiles quantitatively over the long term, taking into account the development and experiences of people with typical development and those with atypical development (e.g., autistic disorders).