This study contrasts the Korean endings used for dog and cat characters with Japanese ones by focusing on the animal character endings on SNS. The results of analysis are as follows; (1) When compared with Japanese, the Korean language has more kinds of animal character endings for dogs and cats. (2) Occurrence environment of Japanese animal character endings is determined by the relationship with sentence-ending particles. Unlike prior studies, ‘-wan’ can be attached to both the front and back of sentence-ending particles and grammaticalization of it is witnessed to be in progress on SNS. On the other hand, occurrence environment of animal character endings in Korean language depends on whether it is connected to the ending of sentences or included in sentences. The latter case is more versatile and grammaticalized than the former. (3) As for the use of animal character endings, Japanese has many types of endings attached to the end of sentences and only ‘-nya’ and ‘-nyan’ have the function of replacing sentence-ending particles. On the other hand, in Korean, the uses of the types inside the sentences are complicated and their functions and attributes differ depending on the kinds of endings.