3 idiots easter eggs that i haven't seen other people talk about but make me fucking crazy
mostly in the order that they happen in the movie
we aren't told where farhan is going and the topic of his flight only comes up in offhand dialogue after this. all we know is that he was supposed to leave india for some reason. on rewatch we can presume he is headed out for one of his wildlife expeditions.
silencer looks up the word for liquor when confronting raju and farhan in the present. he still has not mastered his hindi
additionally, he pops his fart pills in this scene. the farts themselves come later on when he is in the car driving to shimla.
on the topic of silencer's farts, someone graffitied the words "GAS CHAMBER" on his door
farhan throws the bottle of rum at silencer's feet the same way silencer did when he confronted rancho and farhan in the past
the song playing when farhan first arrives at ICE is "give me some sunshine", the song that joy sings when virus tells his father that he will not graduate this year. it's a symbol of things ending-- joy's dream ends and he subsequently kills himself because he will not graduate (the song plays briefly at his funeral as well), and farhan because he is setting aside his lifelong dream of being a photographer to pursue engineering.
farhan brought his camera to university and the first thing he does after checking his room number is take pictures of the dogs on campus. during the birth scene at the end of the film, one of the items used to make the vacuum is a camera cleaning tool, which he's had since day 1.
after joy's funeral, rancho drops the paper with the statistics on india's suicide rates in virus's office as they leave, foreshadowing raju's suicide attempt in the same location later
he does in fact name the inverter after virus. we see this in the second encounter with pia, though it doesn't get used until the scene with her nephew's birth
the ambulance taking over 2 hrs to arrive foreshadows the birth scene where ambulances aren't available either (though then, it's due to flooding of course.)
silencer's secretary came to shimla to make an appointment with phungsukh wangdu (rancho), and silencer shows the photograph with rancho in the background as proof that rancho was in shimla. this is the first hint we get at rancho's real identity
raju jumping from virus's roof foreshadows his suicide attempt (jumping from virus's office) in the very next scene
the run from virus's house into the exam hall foreshadows the way farhan and rancho run when stealing the answer key from virus's office. they're not caught here and have a night of reprieve but raju is punished the next day-- he doesn't get away with this despite running. this is similar to the end when they successfully steal the papers, everyone relaxes for a moment because raju chooses not to cheat. just like raju was caught eventually though, virus turns up at their dorm and expels the three of them.
virus offers to cancel raju's expulsion if he instead writes rancho's name on the expulsion letter instead. however, raju has already said he doesn't want to be expelled because his father only lives to see him become an engineer. it is an especially impossible task for him to put rancho's name instead, because his father is also only alive because of rancho's help several years prior. he thinks about this moment as he's contemplating what to do
raju does not just discard his rings-- he tosses them into a bedpan. this sacrilege shows just how much his personality shifts after his suicide attempt
after govind shaves off his moustache, virus throws the shaving kit out the same window through which raju jumped
virus does not regrow his mustache after the bet with rancho. he is clean shaven for pia's wedding with suhas, indicating that after meeting rancho, virus really did change for life. he isn't even hostile when raju and farhan crash pia's wedding-- mostly, he's just baffled
the way racho dumps out farhan's bag to pull out the letter he'd written to andre istvan mirrors the way that pia dumps out her brother's bag to reveal his suicide note. both boys had a passion for something other than what their fathers wanted for them, but only farhan lived to see it through
"give me some sunshine" plays during their graduation, of course symbolizing the end of their education, but also symbolizing the end of rancho's friendship with raju and farhan. he goes missing immediately after graduation
it's difficult to tell but raju's mother's clothing looks new at graduation, a nod to the previous comments about her not being able to afford new sarees
at the end of the film, rancho is flying a remote controlled plane, similar to the drone he repaired for joy lobo
at the job interview with raju, the interviewer says that "all candidates turn into yes-men" when faced with the job offer. we see this happen at the end of the film with chatur when he finds out rancho's real identity