This line begins another long series of wordplay based on the word “goose,” which is even more obscure than the "solely singular jest" wordplay earlier in the scene. Once again, it’s best if we take you through the lines of text and explain as we go.

Before we dive into the wordplay having to do with our feathered friends, let’s discuss some of the pertinent characteristics of geese.

First of all, if you’ve ever seen a string of geese walking in a line, you would have noticed that no matter how difficult a path the lead goose takes, every subsequent goose follows exactly in its footsteps. 

This gave rise to a popular horse race in Shakespeare’s day called a Wild Goose Chase in which the first rider sets a difficult course while the second rider tries to keep up while following the exact same line. 

A second characteristic of geese is that they are notoriously unintelligent. Most references to a goose imply stupidity. 

And finally, geese are by nature rather mean. If you turn your back on one you’re likely to receive a bite on your rear end.

Now let’s take a look at our first goose jest. Romeo has just urged Mercutio to keep up their battle of wits by using the metaphor of a horse race:

Switch and spurs, switch and spurs; or I'll cry ‘a match’

Mercutio presumes that Romeo is referring to a wild goose chase, and since they are having a contest of wits, it follows that it will be their jests that will be running the race. If that’s the case, Mercutio says, then he’s going to lose:

if our wits run the wild goose chase, I have done I'll lose

According to Mercutio’s reasoning, the racer that is more like a goose is going to win a Wild Goose Chase, and Romeo has five times as much goose, or stupidity, in his wits as Mercutio has in his:

for thou hast more of the wild goose in one of thy wits than, I am sure, I have in my whole five

Mercutio then asks if he has stayed even with Romeo in their race of wits with his clever goose jest:

Was I [even] with you there for the goose jest?

Romeo scores a point when he says that Mercutio is never “even” with him in anything except when it comes to geese, or stupidities. 

Thou wast never with me for any thing when thou wast not there for the goose stupidities 

At this point, Romeo has essentially called Mercutio a stupid goose, so Mercutio pretends to be a goose and threatens to bite Romeo. But since “goose” is another name for a prostitute, Mercutio decides to take on that role and playfully gives Romeo a nip on the ear:

I will bite thee by the ear for that jest

Playing along with Mercutio in the role of a prostitute, Romeo laughingly cites the proverb “A good goose bites not”:

Nay, good goose, bite not

Mercutio, pretending to have taken a bite out of Romeo, describes his wit as a “sharp sauce”: 

Thy wit is a very bitter-sweeting; it is a most sharp sauce

Romeo responds with a sexual innuendo, referencing the proverb: “sweet meat must have a sour sauce”: 

And is it not well served into a sweet goose?

Mercutio then uses a metaphor of cheveril to imply that Romeo has stretched his wit pretty thin. Cheveril is a very soft leather which is stretched out for making gloves. 

O here's a wit of cheveril that stretches from an inch narrow to an ell broad

Making one last goose jest, Romeo turns Mercutio’s comment into another sexual innuendo, playing on the word “it”:

I stretch it out, for that word 'broad’ which added to the goose proves thee far and wide a broad goose.

Well, that was certainly a lot of goose jests — and a lot of sexual innuendo!