On Monday's Tonight Show, Blunt recounted how Kudrow's character was originally named Monica, and having characters with those names (especially when there's a Friends alum involved) led to some hilarious confusion on set.
"We were shooting in Grand Central Station... and we had about 300 extras," the 33-year-old star told Fallon, laughing. "We had actual commuters coming into Grand Central who heard on the loudspeaker, 'OK guys, we're gonna roll on Rachel!' And then they see Lisa Kudrow walking on and then they hear, 'Guys, we're gonna do a close-up on Monica!' And I saw two people have an aneurysm!"
"[Extras] were like, 'It's the Friends reunion!'" she continued. "They were so excited! [And then] disappointed."
BEVERLY HILLS, CA - AUGUST 13: Actors John Krasinski and Emily Blunt attend HFPA Annual Grants Banquet at the Beverly Wilshire Four Seasons Hotel on August 13, 2015 in Beverly Hills, California. (Photo by Frazer Harrison/Getty Images)
NEW YORK, NY - OCTOBER 08: Emily Blunt and husband John Krasinski pose at The Opening Night of the MTC production of Sam Shepard's 'Fool For Love' on Broadway at The Samuel J. Friedman Theatre on October 8, 2015 in New York City. (Photo by Bruce Glikas/FilmMagic)
TORONTO, ON - SEPTEMBER 11: Actors John Krasinski and Emily Blunt attend the 'Sicario' premiere during the 2015 Toronto International Film Festival at Princess of Wales Theatre on September 11, 2015 in Toronto, Canada. (Photo by George Pimentel/WireImage)
LOS ANGELES, CA - JANUARY 15: Actors John Krasinski (L) and Emily Blunt attend the 20th annual Critics' Choice Movie Awards at the Hollywood Palladium on January 15, 2015 in Los Angeles, California. (Photo by Tiffany Rose/Getty Images for Pol Roger Champagne and 1928 Prosecco)
John Krasinski, left, and Emily Blunt arrive at the 6th annual Governors Awards at the Hollywood and Highland Center on Saturday, Nov. 8, 2014 in Los Angeles. (Photo by Chris Pizzello/Invision/AP)
Emily Blunt, left, and John Krasinski arrive at the 72nd annual Golden Globe Awards at the Beverly Hilton Hotel on Sunday, Jan. 11, 2015, in Beverly Hills, Calif. (Photo by Jordan Strauss/Invision/AP)
LOS ANGELES, CA - JANUARY 15: Actor John Krasinski and wife actress Emily Blunt arrive at the 20th Annual Critics' Choice Movie Awards at Hollywood Palladium on January 15, 2015 in Los Angeles, California. (Photo by Jon Kopaloff/FilmMagic)
NEW YORK, NY - DECEMBER 07: (EXCLUSIVE COVERAGE) (L-R) Jon Hamm, Jennifer Westfeldt, John Krasinski and Emily Blunt pose at The Opening Night After Party for ''Elephant Man' on Broadway at Gotham Hall on December 7, 2014 in New York City. (Photo by Bruce Glikas/FilmMagic)
HOLLYWOOD, CA - NOVEMBER 08: Actor John Krasinski (L) and actress Emily Blunt attend the Academy Of Motion Picture Arts And Sciences' 2014 Governors Awards at The Ray Dolby Ballroom at Hollywood & Highland Center on November 8, 2014 in Hollywood, California. (Photo by Steve Granitz/WireImage)
VENICE, ITALY - SEPTEMBER 26: Emily Blunt and John Krasinski are seen on September 26, 2014 in Venice, Italy. George Clooney is set to marry his lawyer fiancee Amal Alamuddin this weekend in Venice where they met. (Photo by Robino Salvatore/GC Images)
BEVERLY HILLS, CA - JANUARY 13: Actors Emily Blunt and John Krasinski arrive at the 70th Annual Golden Globe Awards held at The Beverly Hilton Hotel on January 13, 2013 in Beverly Hills, California. (Photo by Jeff Vespa/WireImage)
SANTA MONICA, CA - JANUARY 10: Actors Emily Blunt and John Krasinski arrive at the 18th Annual Critics' Choice Movie Awards at The Barker Hanger on January 10, 2013 in Santa Monica, California. (Photo by Jeffrey Mayer/WireImage)
SANTA MONICA, CA - JANUARY 10: (L-R) Actors Emily Blunt, John Krasinski and Joseph Gordon-Levitt attend the Critics' Choice Movie Awards 2013 with Champagne Nicolas Feuillatte at Barkar Hangar on January 10, 2013 in Santa Monica, California. (Photo by Tiffany Rose/WireImage)
TORONTO, ON - SEPTEMBER 06: Actress Emily Blunt (R) and husband actor John Krasinski attend the 'Looper' opening night gala premiere during the 2012 Toronto International Film Festival on September 6, 2012 in Toronto, Canada. (Photo by George Pimentel/Getty Images)
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"We were concerned Hazel would be really disinterested," Blunt admitted. "[But] she quite likes her."
In fact, Hazel is already trying to make Violet as comfortable as possible (even if she does so in a hilariously uncomfortable way).
"I turned my back for a second yesterday and I went to the kitchen to make us some lunch and I came back to discover Hazel just dragging Violet off her play mat. Just gently sort of just dragging her," she recounted. "I just said 'Ooh, Hazel, I don't think we want to do that.' And she goes, 'I just want to get her in a better spot.'"
And while Violet is likely still quite a few months away from saying her first words, it turns out Violet had picked up her mother's British accent -- for a while.
"Hazel had my accent for a really long time and would say things like 'wot-ter', which I was really proud of," Blunt shared. "Then, the other day she goes, 'Can I have some waaaaater?' And I went, 'It's wot-ter,' and she was like, 'No, it's water,' and I was like, 'No!'"
After their interview, Blunt and Fallon faced off for an awesome installment of "Box of Lies," where the acclaimed actress manage to pull a few fast ones over on her opponent, but not without getting fooled a few times herself thanks to an "easily pleased" audience.
"He is my perfect man, you know, he is funny and warm and bright and confident and a sort of emboldening person to be around," the actress said of Krasinski, whom she's been married to for six years. Check out the video below to hear more.