Basic Trope: The person who disagrees with the majority opinion is said to be wrong.
Straight: Alice, Bob, and Carol all prefer chocolate — while Dennis prefers vanilla. The others try to make Dennis feel bad for disagreeing with them.
Alice, Bob, and Carol all prefer mint and milk chocolate chip ice cream — while Dennis prefers mint and dark chocolate chip ice cream. The others try to make Dennis feel as if he committed the worst act of blasphemy.
Subverted: The group sit there wearing Death Glares until he gives in and decides to get chocolate... and Alice says "Wow, we were just kidding. You're really suggestible, aren't you?"
Double Subverted: When Dennis adds that really, he'd rather go for coffee instead of ice cream, the laughter dies. "But... this is our Local Hangout. Why would we go anywhere else? I don't like you, coffee-boy. What are you, some kind of hipster?"
Parodied: Everyone in town eats lunch at noon — except for Dennis, who eats lunch at 12:15 PM. The rest of the townsfolk try to get Dennis evicted for not conforming to the town's norms.
Zig Zagged: Alice, Bob, and Carol will sometimes hassle Dennis for preferring vanilla — while, at other times, Dennis will be the one hassling the others for preferring chocolate. Then Alice, Bob, and Carol will defend Dennis — when he gets picked on by an outsider for preferring vanilla. Then Carol reveals that she herself prefers mint — in which Alice, Bob, and Dennis will then hassle her (insisting that both chocolate and vanilla are better than mint). Bob then reveals that he actually likes strawberry the best — in which all four will then finally agree that they don't all have to like the same thing in order to be good friends.
Averted: Even though Dennis disagrees with Alice, Bob, and Carol over chocolate versus vanilla, Dennis is never hassled for disagreeing with the others. It's just a character trait used to subtly mark him out as "the outsider".
It's a propaganda cartoon for an authoritarian regime.
It's an advert for chocolate ice-cream.
Lampshaded: Alice says, "Think, Dennis, there are three of us — and only one of you. Because there are more of us, we are right — and you are wrong. That's called democracy."
Invoked: Dennis prefers vanilla just a little bit more than chocolate — but will exaggerate just how much he prefers vanilla, because he doesn't want people to think that he's a crowd follower. Thus, he will bring up his vanilla preference at every chance he gets.
Exploited: Dennis uses this trope for Reverse Psychology, manipulating the group to think that one course of action is favored by everyone else and then bitterly complaining about it, thus making them all set on doing exactly that.
Defied: Alice says to Bob and Carol, "I see no reason why we can't include Dennis in our group, even if he prefers vanilla over chocolate. After all, we all have a right to our own opinions."
Discussed: Dennis' friend Eva says, "What on earth makes you hang out with Alice's entourage? Tell me, are you actually allowed to have your own personality in that group? I bet they even order the same flavor ice cream..."
Conversed: Ellie says, "I hate shows like this! Why are they trying to tell kids that doing what your friends want is always best?? Maybe they should make an episode called "The Boy Who Wouldn't Jump Off a Bridge"!
Due to Alice, Bob, and Carol's inability to accept Dennis' preference for vanilla, Dennis leaves the group, and gives everyone the silent treatment. When they go back to their day job, their inability to constructively disagree with one another harms business, and they decide We Want Our Jerk Back.
Dennis develops very low self-esteem — because, no matter which opinion he expresses, he is made to feel as if he is in the minority (and, therefore, wrong). He becomes convinced that the reason why he always seems to hold the minority opinion is because he's "dumb", and it doesn't help that various people have actually called him "dumb" just for disagreeing with the majority.
Dennis is forced to go along with the gang against deeply held personal beliefs: For example, Dennis doesn't eat chocolate because he's a Mormon who believes in abstaining from caffeine.
Dennis, who is allergic to chocolate, is pressured into eating it. The rest of the episode revolves around Dennis recovering from an allergic reaction to chocolate.
Alice, Bob, and Carol finally understand how Dennis feels — when they are forced to agree on pizza toppings.
Dennis is a Commander Contrarian, and while the group doesn't mind people disagreeing, they just ignore him because he seems to do it all the time just to get attention. (This may be further deconstructed if it ends up with a Crying Wolf aesop)
Alice, Bob, and Carol understand that not everyone agrees with what people likes, so while they still resent Dennis' personal preference, they agree not to judge him ever again.
Played For Drama: The gang is in a situation where strong group integrity really is more important than making the absolute best decision. For example, Alice is The Captain of The Squad and Dennis second-guessing her orders is compromising morale. Bob is forced to learn this lesson the hard way when he puts his squad-mates in real danger.