The misunderstanding between Vincent Gambini and Judge Haller regarding the two "utes" was in fact a real conversation between Joe Pesci and director Jonathan Lynn, who then decided that it should be added to the movie's script.
When Vinnie is trying to explain his "real name" to Judge Chamberlain, he knocks over the Judge's chessboard. This was accidental, but director Jonathan Lynn thought it was so funny and authentic, he decided to leave it in the film.
The exchange between the prosecutor and automotive expert about the equipment used to analyze the tires was taken almost verbatim from an actual court transcript. The witness, asked how he analyzed the evidence, answered "I have a dual-column gas chromatograph, Hewlett-Packard model 5710a with flame analyzing detectors." The D.A. quipped, "Does that thing come turbo-charged?" and the witness answered, "Only on the floor models." This appears in lots of "funny things said in court" collections.
According to director Jonathan Lynn, the screech owl in the scene at the woods cabin was a real owl which had had a little prior training so that it wouldn't be frightened by the gun-fire noise. The screeches were added in afterward and were artificially induced, and the crew got it to open its mouth by giving it little pieces of beef; but its reaction to Vinny shooting the gun was authentic and needed only one take. "We got amazingly lucky with that screech owl," Lynn says on the DVD commentary.
Shortly after her Academy Award win for Best Supporting Actress, a rumor started circulating that Marisa Tomei had won by mistake because presenter Jack Palance had incorrectly read out the wrong name. This is a highly unlikely occurrence--the Academy specifically has two officials stationed offstage to intervene and read out the correct name if such an event should ever transpire. It never has.
The town square where the exteriors were shot is in Monticello, Georgia. Vinny and Mona stop in front of Lucy's Secondhand Store to check the tire knocking noise. This is an establishing shot for the town they are conducting the trial in and where Mona later gets Vinny's "ridiculous thing" - his red tux. The courthouse in the background is, in real life, Jasper County Superior Court in Monticello. Wahzoo City, Alabama, is a fictional town. However, there is a Yazoo City in Mississippi.
The prison scenes were filmed at Lee Arrendale Correctional Institute in Alto, Georgia. Though depicted in the film, the prison has neither a death row or death chamber facility. The prison was also the setting for the movie Unshackled.
To appear younger, Joe Pesci reportedly wore adhesive straps that pulled back excess skin and wrinkles under his hairpiece, a temporary face lift that gave his face a tightened effect that is very apparent in closeups of him standing on balcony of pig farm adjacent hotel.
According to the DVD commentary, when Gambini says, "Now, Mrs. Riley, and ONLY Mrs. Riley, how many fingers am I holding up now?", Joe Pesci ad-libbed the "only Mrs. Riley!" part. Fred Gwynne's look of embarrassment was real.