Jonny Lee Miller offered to shave his head to look older, but Danny Boyle insisted that Sick Boy retain his iconic blond hair.
While announcing the sequel in an interview, director Danny Boyle joked that he wanted to call it "T2", if James Cameron would allow it (whose film Terminator 2: Judgment Day (1991) is commonly abbreviated as T2). The cast later explained that the title was the one they thought the characters in the movie would have chosen, just so they could annoy Cameron. Since Terminator 2 isn't legally known as T2, Boyle could use the title without permission; however, he settled for T2: Trainspotting, because the internet search term "T2" still lead mostly to sites affiliated with Terminator 2.
Danny Boyle has credited David Bowie with helping to be able to use various hit songs in the original movie inexpensively because he had ties with Lou Reed and Iggy Pop, and helped Boyle out because he was a fan of Shallow Grave (1994). For his own little personal tribute to him following his death, Boyle decided to shoot a moment where Renton goes through his record collection and finds a couple of Bowie's albums. (In the novels, Renton is a fan of Bowie).
Robert Carlyle kept away from his family in Glasgow while filming because he became so much like Begbie.
In Trainspotting (1996), Jonny Lee Miller's Scottish accent was his own. He tested his accuracy in a Glasgow bar stating something along the lines of 'if I could wing it there I was ok'. For this film, however he had a dialect coach, something that Ewan McGregor jokingly put down to Miller not being drunk this time round.
Although this sequel had a substantially bigger budget than its low-budget predecessor, the director and cast all took an equal but lower salary than they were offered, to keep things in perspective. They were offered a share in prospective profits, though.
Although Irvine Welsh wrote a follow-up to his novel Trainspotting in 2002 called 'Porno', this movie follow-up is actually only very loosely based on 'Porno.' It is mostly an original story which includes some unused parts of the Trainspotting novel, and some elements from Porno. That being said, during pre-production, this film was titled 'Porno.'
In Sick Boy's apartment, you can see a DVD copy of 28 Days Later... (2002), which was also directed by Danny Boyle.
This is the first time since 1997 that Ewan McGregor and Danny Boyle have worked together (since A Life Less Ordinary (1997)). The two had a falling out when McGregor was passed over for the lead in The Beach (2000) in favor of Leonardo DiCaprio. McGregor stated they've since reconciled, and he considers the whole matter "water under the bridge".
The four main actors were not all available at the same time at the very beginning of principal photography, due to scheduling conflicts with other projects. Danny Boyle stated in interviews that the American TV careers of Jonny Lee Miller and Robert Carlyle in particular made it a necessity to have a reduced filming schedule that could accommodate all four of the male leads.
When Simon and Begbie first meet in the pub, Simon makes up a story about a mutual friend of theirs traveling to Amsterdam and recognizing Renton. While the character name and situation are slightly different, this is how Simon/Sick Boy discovers Renton's whereabouts in the novel "Porno".
Although a sequel novel to Trainspotting (1996) had already come out in 2002, director Danny Boyle purposely wanted to wait until his cast of actors had aged visibly enough to play 19-year older versions of their original characters. He joked that with actors naturally being quite vain, that could take a while.
In the Italian version, Renton, Sick Boy, Spud, Begbie, Diane, and Gail are dubbed by the same people who dubbed the first movie.
In the opening sequence a cyclist is seen wearing a skeleton mask. This is a direct reference to the Trainspotting novel where skeleton masks were used in the front cover.
In development this film was titled "Porno", named after the sequel novel to 'Trainspotting'.
In the opening scene, a suite version of Lou Reed's 'Perfect Day' can be heard. This song was heard in the original film during Renton's overdosing scene.
The 'prestigious Edinburgh private school' is in fact the main gate of the University of Glasgow.
This is the first sequel that Danny Boyle has directed and the second sequel overall that he has produced (Boyle produced 28 Weeks Later (2007), the sequel to 28 Days Later... (2002)). He was considered as director for the fourth movie in the Alien franchise (which ultimately became Alien Resurrection (1997), but passed on the opportunity over creative differences with the studio, and went on to do A Life Less Ordinary (1997) instead.
The song Sick Boy is listening to in his flat when Renton arrives is Dad's Best Friend by Rubberbandits.
When Renton returns to Scotland and walks through the airport a father picks his daughter up is holding a head bag. The same head bag which Renton filled with all the cash at the end of the first film before walking away.
The opening shot of the movie mirrors that of Trainspotting (1996), only Renton is this time running on a treadmill rather than the streets of Edinburgh.
The subtitles in the American DVD replace some Scottish expressions with their American equivalents such as "little" for "wee."
First time Danny Boyle and Ewen Bremner have worked together since the first film, whilst Boyle has worked with the rest of the group. Boyle worked with Carlyle in The Beach (2000), McGregor in A Life Less Ordinary (1997), and Miller in his Frankenstein stage play in 2011. Funnily enough on the bonus features on the first films DVD, Bremner notes "(Boyle) hasn't hired me since, the cunt".
As Renton gets off the tram early in the film, the blue shirted man on the tram is Ewan McGregor's brother.
Simon's flat is located in Salamander Street in Leith, there is an iconic corner bar opposite called the Pond. Spud's job interview from the first film happened in the factory one street up.
There's a very dreamy song that plays at least twice during the film. Most notably, when Renton is lying on the pool table after meeting Sick Boy in the bar. This song is called 'Deep Blue Day' by Brian Eno, off of his 1983 ambient album "Apollo: Atmospheres and Soundtracks" and was also featured in Trainspotting (1996) when Renton is swimming. Danny Boyle used Brian Eno's 'An Ending (Ascent)' from the same album in 28 Days Later... (2002).
In the original US theatrical run, the first scenes with Begbie and Spud had to be subtitled because their accents were so thick. On home versions, these have been removed. Interestingly enough, distributors wanted to subtitle the entirety of the first movie for this very reason.
It was never made explicit in the first film that it was indeed set in the late 80s like the novel (only hinted upon by the music used). In this sequel, Renton and Sick Boy/Simon use apps that have only really existed as of 2016. Since the events of the first film are said to have happened 20 years ago, it means that both movies take place in the year they were made.
Many 'flashback' scenes were cut from the final cut of the movie. These included more scenes of young Sick Boy and Renton as seen in the movie. They also included 'John Bell' as a young Spud, with actors Conor Mullen and John Gray as a young Begbie.
Immediately before Renton is woken up in the hotel by Simon/Sick Boy's phone call an automated vacuum cleaner in the hallway is shown performing its duties. In A Life Less Ordinary Ewan McGregor's character is made redundant by an automated vacuum cleaner.
Ewan McGregor and Ewen Bremner previously starred together in Black Hawk Down (2001), Jack the Giant Slayer (2013) and Perfect Sense (2011).
While using an ATM with stolen cards, one of the characters says the PIN 1690 with a Sean Connery James Bond (Sean Connery) accent. The characters also used this accent in the first movie in the BB gun scene.
At the start of the film Begbie, whilst talking to his lawyer in prison, states that he's been in prison for 20 years. When he takes Veronica's phone, he seems to be reasonably tech-savvy in operating the phone, as he has been in prison since before smartphones were developed. However he may have had access to a contraband phone whilst he has been in prison.