Certain Let's Plays can change format, pacing, and even tone. Take, for example, seiferguy's LP of Zelda II: The Adventure of Link. The stark contrast between the first and last chapters must be seen to be believed.
In general, a lot of LPers usually tend to start off rather quiet and/or awkward, hardly talking and often leaving a lot of dead air. Some examples of this can be seen in HC Bailly, Lucahjin, and even Protonjon's earliest LPs.
For better or worse, Markiplier is really loud. But even he started out this way, relatively speaking. Compare his original Amnesia LP to his recent Mario Maker videos.
In Nakar's playthrough of Ultima VII Part II: Serpent Isle, Steve the Avatar appears utterly oblivious to the concept of sex, even as the sorceress Frigidazzi is openly trying to seduce her, kiss her, and strip before her. Two games prior, she paid a gypsy lady to have sex with a mouse while she watched. On the other hand, being an utter sociopath has been a firmly established trait since the beginning.
raocow's earlier vids had him sounding dull and tired, with nary a joke in sight. Over time, he evolved into the very idiosyncratic Talkative Loon we've come to love.
He also had a much thicker accent in the early days; in fact, on some of his earliest videos (on Dailymotion instead of Youtube), he can be pretty hard to understand at times, often lapsing back into French. Eventually, he developed a higher-pitched, wackier voice with almost no trace of an accent.
PewDiePie's original talkthrough of "Amnesia The Dark Descent" lacks most of his trademark quirks. Most notably, in the first video he says that he hasn't played a lot of horror games. He also actually collects the tinderboxes, is a lot more scared, has a thicker accent, and isn't constantly yelling. At one point he throws Stephano and runs. Perhaps his most jarring difference is that he doesn't have his rivalry with the "BARRELS!" The Alien Abduction custom story is when he becomes the persona that is either loved or hated by so many for what tend to be the exact same reasons.
Sir Ron Lionheart may be the ultimate example of this trope. Go listen to episode I of his Let's Play of Super Mario 64(-bit), then, say, episode XX, and finally, try episode CXXII and observe the evolution of a legend. OH WHAT THE-! YEAH! FANTASTIC!
Their first video, Two Best Friends Play Kirby's Epic Yarn, which was recorded via camera pointed at the television instead of a video capture device. Their personalities are also radically different, with Pat behaving far more goofishly and Matt being the straight man, with little-to-no gags or humour in favour of just them straightforward bickering at one another.
The first two or so seasons of their machinima series also plays up their routines (Pat as the angry, abusive one and Matt as the dumb, childish, goofish one) far more. They would also feign ignorance on numerous subjects, the most obvious examples being in their Marvel vs. Capcom 3 video. It's jarring to watch their full-length LP's and later Machinima episodes, where they act far more naturally and display a thorough knowledge of video games and the industry, then go back to their Resident Evil 4 episode and watch Matt obliviously and ignorantly dismissing the game as bad for trivial reasons and Pat going into sputtering rages over each and everything he does.
Roahm Mythril actually addresses this trope as "First Game Syndrome". He even lampshades this in regards to his earlier videos, where he sounded like he was half asleep for most of them. Whenever he makes a video updating a Mega Man Perfect Run he's done with new techniques to make the run easier, or to address a mistake he made, he'll insert in the playlist between his earlier videos, usually starting said video with 'Roahm form the future here', and ending it with 'enjoy/we now return you to your de-energized dragon' for the videos that come after it.
Ant Dude 92's Let's Plays on his original channel, Sonik Dude 101 (which is still active, with a large number of his old videos still present) were very different in tone to his newer Let's Plays on his current channel.
His original personality was more sardonic, as he often criticized or made dark jokes about certain game elements (for example, suggesting that Spyro character Hunter is a rapist in Spyro 2: Ripto's Rage). He often used harsher language when getting frustrated, sometimes screaming in anger, and had less of a connection with his audience. Also, the video quality of his older videos were poorer than the high-definition, well-edited Let's Plays he uploads now.
Nowadays, he has an upbeat, welcoming, family-friendly personality, very rarely swears or gets frustrated (instead seeing the humour in failure), and rarely makes criticisms towards the games he plays. His videos now have brighter colours, intros and outros, and have numbered video thumbnails. Lastly, he reviews games, both new and old, more often.
Let's Play Minecraft's Early Installment Weirdness is the series' first ten episodes. At the beginning, only Gavin Free knew how to play Minecraft and would constantly troll the other AH members. The Tower of Pimps was a creation of that trolling before it became a MacGuffin for the series. Achievement City was a troll attempt on Jack Pattillo by Geoff Ramsey and Gavin before it became their starting hub. They wouldn't get their trademark skins until episode 10, when the events and the Tower of Pimps became commonplace. Jack, Geoff, Gavin and Michael Jones are the only four members still around — Ray Narvaez Jr. was also one of the originals, but he left in early 2015, and Caleb Denecour was the group's Sixth Ranger for the early days until a cheating incident led him to being pushed out and replaced with Ryan Haywood.
Like with Minecraft, Let's Play Grand Theft Auto's EIW is within its first few episodes. Most of those were both Things to Do In and just screwing around in Grand Theft Auto IV. It wasn't until they started doing "Cops n' Crooks" that things would begin to go into the "Let's check out the game modes on this thing", also, they only stayed on GTA IV for a few months, essentially waiting for Grand Theft Auto V to come out.
Chuggaaconroy, like many LPers, was rather quiet in his earlier videos in comparison to his No Indoor VoiceLarge Ham style he adopted in later ones. He's also far less informative in his earlier work, to the point where he didn't even one hundred percent a few of his earliest LPs, as opposed to how he always goes for one hundred percent in his later LPs, as well as showing off everything that possibly could be shown off in them. His Paper Mario playthrough assumed that viewers were familiar with the rest of the Paper Mario series, starkly contrasting the Chugga that keeps future installments' events secret and takes care to avoid spoiling anything. Also, his trademark puns he's (in)famous for are also almost completely absent in his earliest works, where he chose to reference YouTube Poopmemes more often than anything else. Furthermore, he was slightly more open to heavier swearing, which could surprise anyone used to his current Gosh Darn It to Heck! tendencies upon hearing him drop an f-bomb in his EarthBound & Super Mario RPG Let's Plays and his Mega Man 9 one-off.
On the topic of that last part, Chugga's earlier years featured a rather notable amount of miscellaneous videos, with one of them being the first video he uploaded on his channel. His "Fifty Facts" video was removed after some of the eponymous facts became outdated, and most of his 2008 Pokémon Platinum videosNote Not to be confused with his 2016 LP of the game. were removed because he was disappointed with their quality (they were recorded on a camcorder). However, most of his miscellaneous videos are still up on his channel, buried between his earlier Let's Plays.
Kurtjmac didn't actually intend to go to the Far Lands in Minecraft at first; the first 13 episodes of Far Lands or Bust are just a standard let's play of Minecraft. Kurt is also considerably more quiet in his early videos than he is now.
The first year of Game Grumps consisted solely of Arin playing games with Jon. Barry and Suzy were often mentioned but never seen. The spin off series like Steam Train, Table Flip, and Grumpcade didn't exist. Danny, Ross, Kevin, and reoccurring guests like Markiplier and ProJared weren't in the original series either. It was after Jon left the show in 2013 when new members and shows were being introduced.
Patterrz's earlier Pokémon playthroughs are weird to watch now, since he is overall much slower and calmer. It wasn't until his Emerald Eliminationlocke that he began to be much more upbeat during the entire run and talked louder.
Zero9teen, one of the earliest Let's Players on YouTube, initially started out making videos of him messing around in the Dead Rising demo. His first true Let's Play on Sonic 3 & Knuckles utilized Emulation, while most other videos involved the age-old method of filming the television screen with the camera. Eventually, he started recording gameplay footage for his Let's Plays using a capture card, and after several long hiatuses, nowadays streams live on his Twitch account.