There are several instances in the play of metaphors drawn from the animal kingdom. Animals which Elizabethans would have known in a domesticated context are used to express restrictions on power. Luciana believes that Antipholus is within his rights as Adriana's husband to "bridle" her will (Act 2, scene 1, line 13). But Adriana thinks it is foolishness to submit so easily: "There's none but asses will be bridled so" (Act 2, scene 1, line 14). Luciana continues her argument with more references to animals, this time wild: "The beasts, the fishes, and the winged fowls / Are their males' subjects, and at their controls" because the male, "more divine," is by God's design "the master of all these" (Act 2, scene 1, lines 18-20).
Dromio S., in an attempt to explain why others whom he does not know should seem to know him, thinks that he must have been transformed by magic into an ass or an ape. Both animals carried connotations of foolishness, showing that Dromio believes he is being made a fool of. Dromio also fears (in Act 3, scene 2, line 145) that the kitchen maid Nell is a sorceress who will change him into a "curtal dog, and made me turn i'th'wheel." This is a reference to the dock-tailed dogs that were put to work in Shakespeare's day treading a wheel that turned a spit to roast meat. The image is one of grinding servitude - that is, loss of power.
The same water drop metaphor is used by two characters in the play to explore the theme of identity. In Act 1, scene 2, lines 35-40, Antipholus S. likens himself to a drop of water that has plunged into the ocean to seek another drop (his twin brother and mother), losing his own identity in the process. In Act 1, scene 2, Adriana takes up the metaphor to express her view that husband and wife are as indivisible and that the absence of one irreparably takes something away from the other, just as a drop of water placed into the ocean cannot be retrieved in its integrity. Her idea of married love is possessive and demands the obliteration of all individual identity.
In Act 3, scene 2, line 46, Antipholus S. rebukes Luciana for trying to make him feel guilty for abusing Adriana's trust (Luciana mistakenly believes Antipholus S. to be Adriana's husband). He asks Luciana not "To drown me in thy sister's flood of tears," a reference to the loss of his own identity through Adriana's possessive love as well as, more generally, to the loss of his identity through confusion with his brother.
The water image ties in with the background story of the forced separation of Egeon's family and the two sets of twins by means of a shipwreck at sea. The ocean is vast, and a drop of water is minuscule, heightening the sense of the impossibility of the family's reunion and the miraculous nature of that reunion when it finally happens.
Dromio S.'s extended comparison of the body of the (as he says) fat and unattractive Nell to the globe of the earth and the parts of her body to different countries has one purpose only, to make the audience laugh (Act 3, scene 2, lines 111ff.).