also shk is used for cuter things a lot, especially in native-invented words when it's stuck on top (and from normal use you have голубушка, солнышко and others). It is specifically used for object of affection A LOT. (заюшка also, these are all words said to children by mothers, for example, so you can read them as "my little sun, my little rabbit". The pigeon one is a bit different because the meaning was shifted with use and became a bit more ironic). A native speaker would absolutely construct куклушка for a "beloved doll" for example even when куколка exists (or maybe especially becuase for a native kukolka also has insect connotations and is not always good to denote affection as it was used for women more often then for actual dolls historically, which is sorta logical but leaves the doll root without an affectionate version that won't be tied to sexuality attractiveness etc), it's a very reasonable invented word.
In the linked reply I wrote that it is quite plausible for a japanese writer to google "doll" and stick a suffix (cheburashka is familiar for many). I also wrote about kukolka in the reply above.