There is a fine line between being the comic and being the nuisance. It's all too easy to forget the opinion that matters is the audience, not the comic. Even if everyone loves your work, you will always have detractors. It's when all you have is detractors and yet you still persist in your antics are harsher measures called for. Pippin never learned this.
Pippin was supposed to be part of the comedy team with Merry. Two chaotic hobbit thieves with larceny on their mind and a snippy remark on their tongues. They started harmlessly enough, simply stealing fireworks and laughing about it. When they were finally introduced into the actual campaign it was in the middle of a vegetable heist, and they were able to show of their stealth skills with an intentional easy escape from the Nazgul. You would think a quartet of hobbits moving their full speed wouldn't even make a mounted Nazgul sweat, but the DM let them get away for dramatic purpose.
Unfortunately this made Pippin think he was invisible. In short order he openly gives away the secret quest to the first people who actually asks him about, bringing the wrath of the Nazgul on him and getting a man killed in the process. Pippin doesn't care, and doesn't even change his ways even after Aragorn tries to set them straight. When Gandalf shows back up and reassumes command, Pippin still thinks since Aragorn put up with him, the much more veteran player Gandalf would as well. Pippin thought wrong.
Pippin finds that Gandalf is not stoic like Aragorn, and doesn't brook mischief well. After being rebuked by Gandalf for interrupting his thinking, Pippin spends the rest of the time chucking rocks into the water and giving away their position. After the Watcher in the Water nearly TPK's the lot of them, you'd think he would learn. No, just a few minutes later after Gandalf gives the explicit advice DO NOT DO ANYTHING, Pippin up and does something. After another fight in which Frodo nearly dies except for DM enforced plot armor, Pippin still hasn't learned anything except Gandalf really, really doesn't like him. Fortunately for Pippin, the likelihood of finding himself abandoned and tied upside down to the first tree they find outside of Moria is reduced when Aragorn 'forgets' to throw Gandalf a rope.
Since Aragorn doesn't really care if the hobbits live or die, Pippin goes under the wing of Boromir, who had been training them earlier. Gimli isn't the kind to hang around new players and Legolas can't have the hobbits cut into his preening time. Unfortunately Aragorn does the math, and if the four hobbits side with Boromir then Boromir is the new defacto team leader. Now that Boromir is between Aragorn and a leadership role, and the DM and his shot at Frodo's player, he isn't long for this game either. While Merry and Pippin show they can actually fight, the fix is in as every Uruk Hai concentrates on Boromir, despite taking casualties from the two hobbits. Eventually Merry and Pippin are captured while Boromor starts looking like he's cosplaying Shuna Sassi.
As Pippin and Merry are carted off, Pippin fails to realize that Merry is actually roleplaying and annoys the crap out of the Uruk Hai until the game slows down so Merry can actually figure out what's going on. Merry realizes there is no rescue coming, and they escape as soon as the Rohirrim distract the orcs by killing all of them. After a brief chase by an orc boss, the DM has to kick the two back into the plot by having the tree they climb actually turn out to be an ent who physically carries them to the next plot point. Even though the DM tries to write the two out of the story by having Gandalf instruct them they go far, far away and never come back, Pippin decides to head to Isenguard even though he doesn't have a clue Saruman has actually done something to enrage the ents. The DM realizing Aragorn is completely off script now ends that plot point by having the Ents clean out Isenguard.
Finally reunited with the rest of the party except for Frodo and DMPC Sam, Pippin spends approximately one night before screwing up so badly Gandalf decides to personally take him under his wing before Aragorn forget to throw him a rope as well. Pippin finally starts actually playing the game instead of doing random stuff and making snide remarks. He's put through a series of minor tests, like climbing onto the beacon, sneaking past guards and even trying to use diplomacy on Denethor. He botches the last one badly, but two out of three aren't bad.
When Sauron's army finally shows up, Pippin realizes just how disposable he is, and that Gandalf didn't actually hate him. Sure Pippin annoyed Gandalf to the point of madness, but Gandalf finally noticed Pippin wasn't trying to be annoying, but he'd never roleplayed before and had no idea what to do. When the orcs assaulted the upper levels of Minas Tirith Gandalf lets Pippin know combat for the first real time on his own. While Gandalf slaughters the first nine orcs he sees in a single turn, he holds off one action so Pippin can get a shot in. Finally Pippin realizes it's about team work, even if the epic fighter's body count has reduced Sauron's army by several percentage points by himself, he hasn't hogged all the kills.
Pippin gets his chance to show what he has learned under Gandalf's tutelage. Rather than run and hide when Denethor fails his sanity check, he gets Gandalf instead so they can save Faramir together. Gandalf lets Pippin do all the heroics, and after a crash course in a hobbit's allergic reaction to the encumbrance rules, Pippin saves Faramir by himself. A major victory in the roleplaying history of Pippin's player.
So while Aragorn gets a kingdom and wife, Legolas gets to drag his people to a victory party they did little to help accomplish, Gimli makes bank selling priceless spell components in Galadriel's hair and Frodo probably gets a restraining order against Sam, Pippin gets to go home with Merry. While Merry has risen to the occasion without help or prodding, Pippin is ready to try again as well. This time a bit more mature and hopefully a lot less useless.