bobsey twins, n. — Green’s Dictionary of Slang

bobsey twins n.

[the children’s adventure story characters created 1904 by ‘Laure Lee Hope’ (Edward Stratemeyer) + ref. to UK bobby n.¹ (1)]

(US camp gay) the police, when working as a pair.

1972		B. Rodgers Queens’ Vernacular 126: Two cops making their beat in a prowl car are the Bobsey Twins.
1980		Maledicta IV:2 (Winter) 230: If they travel in pairs [...] they are sisters (nuns), Bobsey twins, etc.