The suffix "-chan" is ubiquitous in anime, but most English dubs don't carry it over into the translation. Even if Chris had heard it before watching Excel Saga, the sheer abundance of "-chan" combined with the first syllable of a character's name in the series is probably what led Chris to dub himself "Chris-Chan". This would also explain Chris's failure to realize the context of -chan. While the honorific is used for children, girls, and young women, Excel Saga uses it so gratuitously that a viewer might never notice the pattern, especially in this episode. Nevertheless, the suffix "-chan" could be seen as working for Chris in a unique way, since it effectively puns off his last name: "Chandler".