Delivering groceries or cleaning airports, mobile robots exist in public spaces. While these examples showcase robots that execute tasks, this paper explores mobile robots that encourage posthuman collaboration rather than managing environments independently. With feigned fragility, cuteness and incomplete functionalities, the so-called "weak robots" invite passersby to engage not only on a utilitarian level, but also through imaginative and emotional responses. After examining the workings of "weak robots" by queering notions of function and ability, we introduce two speculative design fiction vignettes that describe choreographies of such robots in future urban spaces -- one exploring a utopian weak robot and the other a dystopian weak robot. We introduce these speculations in order to discuss how different values may drive design decisions, and how such decisions may shape and drive different socio-technical futures in which robots and humans share public spaces that incentivise collaboration.