@q@darkphoenix@kitten@elizabeth.cat@erincandescent of course German can get things that end in -chen that aren't diminuitives and ones that are but where the original form is obscure and so on...
a Kuchen (m) is not a -chen a Mädchen (n) is a -chen but the originating word is out of use and of course -chen can just be a -n plural of a word ending in che like Küchen or a nominalized verb form of a verb with a stem that ends in ch like Lachen (n)
Hard to say without knowing precisely what you intended to write
- The Subjekt is "ich", so the declension you want is "bin" instead of "sein" - I don't think "werde" would typically be used like that in German. It might be technically valid but I don't think it's traditional
"aber vielleicht bin ich morgen ein Kätzchen" is my guess? But (a) I'm also a learner and (b) I don't know precisely how you wanted to phrase it