Sentence:  It was quite a conincidence for a mechanical sea creature and he was speculating whether it could possibly have been done on purpose when Katsu stole his other sock and flopped on to the floor with an unbiological bang, whereupon it <WSD>octopused</WSD> out of the open door and slid down the banister. 
Meaning of the word marked with <WSD> tags:  To behave like an octopus.