The first time we see Snatcher, he's leading a cheese hunt. We'll note that cheese hunts are both "cruel and… illegal" (3.8) according to Grandfather, though this fact doesn't stop Snatcher from pursuing helpless cheeses as part of his greater plan to dominate Ratbridge.
When Snatcher notices Arthur spying on them, he sets his goons and dogs after him, saying, "'Get the little tyke!'" (4.17), and when he does, we sense that Snatcher doesn't have nice things planned for Arthur. In other words, within moments of meeting this character, we understand that he's not very nice, and he definitely doesn't want anyone or anything to stand in the way of his plans. So when he calls Arthur a "'little vermin'" (4.21), we add "verbally abusive" to his quickly growing list of undesirable characteristics.
It's not very surprising, then, when Snatcher starts issuing threats. If anything, it seems to be a personal passion of his, whether he's demanding Arthur hand over his wings by saying, "'Get 'em off quick, or I'll be setting the hounds on yer!'" (4.27), or telling his Cheese Guild members to be sure to capture a lot of cheeses on a hunt:
"We must get all the cheese we can tonight. I don't want any slacking. Anybody I catch not pulling his weight may find themselves in 'reduced circumstances.' Get my drift?" (19.36)
The threat Snatcher makes here is to shrink anyone who doesn't work their hardest to bring in more cheeses by using the handy dandy resizing machine he has in this possession. It's a terrible threat to make in its own right, but the cheese Snatcher's so eager to get his hands on is connected to perhaps the most threatening thing about Snatcher: Framley.
What do we mean by Framley? We're talking about the Great One, a.k.a. a resized rat named Framley, who they feed cheese as they enlarge him, turning the rodent into a war machine in hopes of taking over Ratbridge and ruling the town. As Snatcher so eloquently puts it:
"We're going to use the big rat to clobber them what done us down, blow up the council offices, rob the bank, knock down the factories, and then start flogging dodgy cheese again!" (48.24)
We're hard pressed to think of something more threatening than an enormously oversized rat.
Snatcher is a clever guy. We certainly wouldn't want to be pitted against him. He bribes the police force of Ratbridge to let him have his way, and he has the women of Ratbridge practically eating from the palm of his hand.
It takes Arthur a hot minute to figure this out, but Snatcher is cross-dressing as Madame Froufrou in order to make money off the mini-critters that his evil plan generates. In Arthur's defense, though, Madame Froufrou rocks a one-of-a-kind look. Check this style star out:
She wore a dress that looked as if it were made from skinned sofa and cardboard, an enormous pink wig, and a pair of rubber gloves. She also had a patch over one eye. (13.5)
Effie Trinket much? The town ladies who worship Madame Froufrou refer to her as "the fashion princess" (13.7), and she claims to bring them pearls of wisdom from "'the finest ladies of Pari'" (13.20), though she is actually just making stuff up. Hexagonal buttocks? Miniature monsters as pets? C'mon ladies, stop being so gullible.
But it seems like Snatcher's spent a while earning their trust, because they eat up every word and come back for seconds… and thirds. Madame Froufrou isn't some new chick in town; she's their tried and true style guru. The willingness of town ladies to follow her, though, shows us that they prioritize external appearances and the opinion of their peers over, well, just about everything else. Otherwise they wouldn't be such easy prey for Snatcher's mind games.
The town ladies' shallowness works perfectly for Snatcher, though, who has figured out a way to turn fashion into a profitable prestige game. As Madame Froufrou, he tells the assembled ladies in the market:
"I shall do what they do in Pari. I shall do what is the latest thing… and select only from those who are… fashionably… RICH!" (13.35)
And when Snatcher does this, not only does he make it sound like being fashionable is the only goal that women should have in life, he inspires these vain ladies to clamor for his goods, thereby supporting his whole shrinking-creatures habit. He says that those who aren't fashionably rich "'must cast yourself from this world of glamor and retire to your true miserable and rightfully low position'" (13.36), which is pretty clever. After all, nobody wants to believe they belong at the bottom of the social heap.
Snatcher gets away with this little scheme for a while, until a real Parisian lady comes to town and corrects all the damage he's done. Fact-checking is the enemy of lies, friends.
According to Grandfather's tale, Snatcher was the son of a big name cheese industry guy. But when Snatcher's dad got sued for unethical cheese-making practices and lost his fortune, Snatcher got tossed into public school. As Herbert characterizes it: "'He didn't take his fall from Ratbridge society well. Hateful little snob!'" (39.25). Given what we've seen of Snatcher, we have no trouble believing that he didn't adjust well to this change.
This fall in social fortune led to Snatcher becoming a jerk at school: bullying, bribing, and cheating his way to top grades and high status once more. Grandfather sums it up by saying, "'On the strength of a bit of blackmail and his stolen results, he got a scholarship to Oxford'" (39.31), which seems like it's pretty much been Snatcher's game plan ever since. Remember: The reason Arthur and Grandfather live underground is because Snatcher poisoned an opponent in a card game at the Nag's Head and framed Grandfather for the crime.
In short, Snatcher will do anything to get away with the crime without doing the time.
Of course, the combination of Snatcher's sense of entitlement and his awareness of his cleverness leads to a bit of vanity, which we can understand as a chink in his armor. This is how Willbury gets Snatcher to reveal his evil plan: by complimenting him. After Willbury says, "I'm sure your plan must be rather good" (44.22), here's how Snatcher responds:
Snatcher puffed up a little as his vanity took over. (44.23)
And then he spills the beans about turning Framley into his war machine. Willbury didn't even have to try very hard.
In the end, Snatcher's plans are foiled by Arthur and his friends. Snatcher himself makes a getaway, covered in cheese like the rest of the townsfolk and escaping notice until it's too late. We wonder what kind of evil plan he'll cook up next…