GRUMIO, to Hortensio
I pray you, sir, let him go while
the humor lasts. O' my word, an she knew him as
well as I do, she would think scolding would do little
good upon him: (1.2.108-111)
When Grumio notes that Katherine doesn't have a chance against Petruchio, he lets on that perhaps Petruchio's (future) transformation from an average guy to a domineering bully, who is more of a "shrew" than Kate, is more common than Petruchio lets on. It seems that P has played this game before.
GRUMIO
I'll tell you what,
sir, an she stand him but a little, he will throw a
figure in her face and so disfigure her with it that
she shall have no more eyes to see withal than a cat.
You know him not, sir. (1.2.113-117)
When Grumio assures Hortensio that Petruchio will beat Kate in a verbal battle of wits, he suggests that Petruchio's words, his "figures" of speech, have the power to physically alter Kate's appearance. (Like acid might burn and transform a person's face.) This anticipates Kate's transformation from railing shrew to an obedient wife. And though Petruchio never lays a hand on Kate, his taming tactics – starvation, forced sleep deprivation, etc. – do cause Kate to physically suffer, just as acid would.
Quote 3
GRUMIO
Tell thou the tale! But hadst thou not crossed
me thou shouldst have heard how her horse fell,
and she under her horse; thou shouldst have heard
in how miry a place, how she was bemoiled, how he
left her with the horse upon her, how he beat me
because her horse stumbled, how she waded
through the dirt to pluck him off me, how he swore,
how she prayed, that never prayed before, how I
cried, how the horses ran away, how her bridle was
burst, how I lost my crupper, with many things of
worthy memory, which now shall die in oblivion,
and thou return unexperienced to thy grave. (4.1.67-78)
Here's yet another narration of an off-stage event, this time by Grumio. The curious thing about this moment is that Grumio gives Curtis an elaborate description of a scene after he tells him he's not going to say anything. Grumio's dramatic description of what must have been a terrible experience for Kate manages to turn the awful scene into a highly comedic moment.
Quote 4
GRUMIO
"Katharine the curst,"
A title for a maid of all titles the worst. (1.2.130-131)
Grumio's insistence that being labeled a shrew is the "worst" fate a woman can suffer is odd – we're used to hearing that being labeled a "whore" is the worst reputation for a woman in Elizabethan comedy.
Quote 5
GRUMIO
Nay, 'tis no matter, sir, what he 'leges in
Latin. (1.2.30-31)
When Grumio (who is supposed to be an Italian character like the rest of the cast) thinks that Hortensio and Petruchio have greeting each other in Latin (they actually spoke in Italian), he reveals his lack of formal education. Makes sense, he's a servant, not an upper-middle-class character. This little joke is also directed at Shakespeare's audience, many of whom also didn't know the difference between Latin and Italian.
Quote 6
GRUMIO
O this woodcock, what an ass it is! (1.2.161)
Grumio (Petruchio's servant) remarks disdainfully that Gremio (an older suitor of Bianca) is inappropriate in his quest to wed Bianca. The play and the characters take a lot of pleasure in duping Gremio as punishment for his desire for a much, much younger woman.