In "Deep Trouble for Sam", after witnessing their Uncle Sam stuck in soil, James questions the possibility of drowning in soil, to which Sarah replies, "Don't says things like that!" This was more just concern for her uncle - she had undergone a similar experience in "Lost in the Fog" so she may have had a greater effect for what her uncle was feeling right now.
As of Series 5, Trevor is no longer an auxiliary fireman, which is unexplained. But then, considering Trevor's fear of heights, there is a possibility that it could be contributed to him leaving the post. Also, Trevor has already got his hands tied with his main job of driving the bus as well as making deliveries so it's also possible he no longer has the time to contribute his services to the fire brigade.
It may have also lead to Penny's transfer to Pontypandy in the same series.
When you look at the upgrades to Jupiter and Venus in Series 5 and compare them to the models in the original series, there is the possibility that they were not simply upgrades but completely new fire engines. It's likely that the old engines were starting to show their age and couldn't keep with the times so these two new fire engines were their replacements.
Considering Wallaby 1 was replaced by Wallaby 2 in "Alien Alert", that's an even bigger possibility not to mention Trevor receiving a new bus after his old bus fell over the cliff in "Ultimate Heroes".
In "Wheel of Fire", Elvis is notably absent, leaving only Sam, Penny, and Steele at the fire station. Bronwyn mentioned that in the past, she would watch Gareth's disastrous fireworks shows with her cousin Liam, so whatever this occassion was (likely Guy Fawkes Night), Elvis could have been away, spending it with Jerry Lee in Newtown.
"Wishing Well" has another example of Fridge Horror. After Norman fell into the well, his mother was deeply worried, which prompted to Trevor to launch a search party. Had this not happened, it's possible that Norman would have been trapped down that well forever.
When you think about the times when Norman saved Sarah and James in "Snow Business" and Trevor in "Trevor's Bus Boot Sale", let's imagine a world where Norman didn't exist. Neither the twins nor Trevor would have survive because by the time they were found it would have been too late.
As for the former example, when you consider how close Sam is the twins, it's possible that he may have even become heavily depressed in this alternate universe due to their deaths and this would have taken a toll on his job. So, he ended up leaving the job he loved so much.
Sarah's predicament in "Lost in the Fog" was terrifying. Not only were she and James lost in the fog miles from the nearest telephone but Sarah fell into quicksand-like mud. It was lucky for her that Sam and Penny were searching. Had Sam not been there to James' cries for help, Sarah would have died.
This also serves as Fridge Brilliance when you consider Sarah's reaction to seeing her uncle in a similar predicament one series later, as stated above.
When you look at "Deep Trouble for Sam", you realise just how serious Sam's predicament truly is. He fell into a mine where there would been high levels of poisonous gas, not to mention all that soil that fell on top of him. So when he dug his way out, it's possible that his coughing was a result because of the effects it had on his breathing. Had the fire brigade not arrived in time, Sam would have surely perished.
Add to that, the incident occurred because Sam and Trevor offered to un-weed Penny's new garden while she was filling in for Sam, and Sam was only saved because Trevor came as arranged and called the fire brigade. Imagine if Penny had at some earlier point just decided to do the job herself and no one was around to help.
This also makes "Norman's Pitfall" all that more horrifying because had Rosa not shown up and revealed the mine's entrance, Norman, Sam and Elvis would have also died due to a limited supply of oxygen.
"Treehouse Trouble" has yet another example. Had Trevor, Mike and the kids fallen, they would have either been killed and had life-changing injuries.
“Froggy Fantasy” has the fire come very close to the door where James was locked in. Thank goodness Sam put out the fire when he did or things would’ve been much worse.
In "Poorly Penny", Station Officer Steele tells Penny, as well as Sam and Elvis, that Working Through the Cold puts themselves and others in more danger. However, a few seasons later in "Froggy Fantasy", Elvis still rocks up to work despite having a cold and, as expected, ends up putting himself and others in danger due to his sneezing. However, instead of advising him to take a sick day, Steele is extra hard on him during the drills and ensuing rescue, insisting that a firefighter always completes a drill to the best of their ability no matter how sick they are. Elvis probably came in despite having a cold to avoid letting Steele down, and he still got reprimanded for it. It's a wonder he isn't completely terrified of the guy at this point.
