It’s a truism in Shakespeare that if it’s even moderately important for the audience to know, he makes sure it’s said around three times. Theories tend toward practicality here: you can’t expect attentive comprehension from an audience of unruly midday inebriates with one eye out for prostitutes and snacks. And that’s just the nobility – the groundlings were noisy as well.
This makes editing Shakespeare a little easier sometimes – a front-facing, seated audience trained to do its shopping at intermission can usually do with one or two mentions of the fact at hand, so the trimmer can just prune out the least useful instance(s). Unless it’s a mug line, of course. Merch people hate it when you cut out the line they put on the mug.
All that said, there’s an instance in Errors of information sort of sneaking in only once and while I know of no one who gets that upset about missing this detail, every now and then people do bring it up.
To wit: why on earth do the twins all have the same name?
Parents of twins have been known to do the matchy-matchy thing with clothing for a long time, and it’s something twins have been known to continue well into old age even without parental enforcement. But sharing names is a bridge too far.
The easy answer is that they didn’t give the twins the same names. Because that’s a terrible idea.
Late in the important expository info loaded – and I mean loaded – into the play’s first scene, Egeon says of the twin he raised that he
At eighteene yeeres became inquisitive
After his brother; and importuned me
That his attendant, so his case was like,
Reft of his brother, but retain’d his name,
Might bear him company in the quest of him…
(Sidebar: the twistily-worded phrase “so his case was like” would roughly translate to “so similar was his situation”.)
And there it is: “retain’d his name,” Egeon says blithely, never to be discussed again, even by the twins when they meet up at the end.
In Shakespeare’s main source for Errors (the italics are important here – his main source for just plain errors was Holinshed. ZING!), Menaechmi by Plautus, this is all laid out nicely by the speaker of a prologue, who says that when news got back to Syracuse of [the broadly different situation that separated the twins in the original], the man raising the “surviving” twin changed the boy’s name to that of his lost sibling – no particular reason is given, but it was likely as a sort of memorial.
That prologue continues with a useful couplet stating (in the Nixon translation in my battered ol’ Loeb copy) “To keep you from going astray later, I herewith forewarn you:/ Both twins have the same name.” Couldn’t ask for more than that. I guess the Romans were drunk, too. Hooda thought?
It’s not clear how this worked in Shakespeare’s Errors. Were the names of the Syracusan pair changed in infancy? Did they choose to do it themselves when the non-servant lad “became inquisitive”? Does anyone really care that much as long as the requisite wackiness ensues?
I suspect the latter is the best answer. As with most of Shakespeare’s comedies, those details didn’t seem very important to him, so we honor them best by steamrolling over them apace and hoping no wiseacre ever makes a living picking the plays apart word by word in the printed form they were never intended to take. Best of luck.