Milton's ramblings about his stapler are actually accurate. The Swingline brand stapler is a far more reliable model than the cheaper, flimsier Boston brand. Also counts as Fridge Horror when you realize that you've been working a white collar office job long enough to appreciate that.
The cake scene also makes sense in regards of Milton once you realize that Milton has ceased being an actual employee long before that point.
During the opening credits we see Michael listening to gangster rap, which is very different than the soft pop music Michael Bolton is known for, so it makes sense that he wouldn't like his music.
Milton's boredom at that resort makes sense: no matter how rich you may be, having no one to share it with will leave you depressed and empty.
Playing off the top fridge entry, how the hell did Milton even afford to go to an exotic place in the end? Simple, he saw the letter with the check Peter had the returned money in it. He already committing arson, what is one more felony?
Tom managing to hold a job despite not being that skilled at it makes a good deal of sense: considering his age, Tom might have entered the corporate world at a time when benefits were far more guaranteed and when it was common for middle managers to hold ridiculous amounts of wealth despite not having skills. In this environment, Tom wouldn't be incentivized to broaden his skill set since he would expect a pension and benefits for doing the same job over and over again.
Doubles with Fridge Horror that the Bobs are impressed with Peter because he recognizes his work is pointless and doesn't care beyond his own benefit. As such, he has an awareness of his surroundings that they share. This implies the executives have an equal amount of contempt for the office and its drones' struggles.
The Bobs' downsize rampage is targeting the company's brightest and most motivated, leaving the jaded and lazy. This will undoubtedly result in exponentially more overtime demands of the staff least happy to be there in the first place. These idiots were hired to help Initech, but they are actually grievously sabotaging it... and probably pocketing obscene consultant fees while doing it.
The fact that the Bobs have the authority to threaten Lumbergh implies even worse: that Initech doesn't care what happens at this office. Corporations such as Initech were even then working branches to oblivion, forcing everyone to quit, get laid off, or accept increasingly difficult working conditions until simply closing the building the moment it's more profitable to cut it loose.
The Bobs were hired to ax staff when higher-paid management was clearly redundant, and potentially the primary source of waste at Initech.
Peter is nagged about his TPS reports by no less than five people - Mike, Sameer, Lumbergh, Dom, and another boss. Later on, he reveals that in fact, he has eight bosses, all of whom hassle him for every single little screwup. So that means that he was nagged five more times offscreen.
Milton is not just neurotic, he's a full-blown sociopath. It's easy to miss due to his Cloud Cuckoolander ways and gawky mannerisms, but he burned the place down just like he said he would.
Milton never even knew he was fired by the time he pulled his arson. He did it because he was that pissed off.
Actually, if you listen closely during the fire scene, you can hear him mention that they fired him. Presumably, he found something in Lumbergh's office that revealed the truth.
With all of this considered, poisoning the resort's guacamole with strychnine was likely not an idle threat.
Although it was played for laughs, this would have been a hideous scenario. Think of how many people are snacking on guac at that kind of a resort. Suddenly, people start vomiting, spasming, and writhing on the sand in agony. Many would be dead by the time anyone figured out what was happening.
