Guys, we don't mean to alarm you but '13 Going on 30' is fifteen years old today. We don't believe it either.

The body swap movie has had recent outings in the likes of 'Shazam!' and 'Little'. But '13 Going on 30' is, in our opinion anyway, up there with 'Big' as one of the best of the bunch.

For those of you in need of a refresher, the comedy follows a 13-year-old named Jenna who upon making a wish on her birthday flashes forward into her 30-year-old body. Which is Jennifer Garner - so who's complaining, really? The movie also stars Judy Greer and Mark Ruffalo in one of their earlier roles, and Andy Serkis plays Jenna's boss.

Directed by Gary Winnick, it's a classic and if you haven't seen it, it's on Netflix, so you've no excuse!

To mark its anniversary, please enjoy these fascinating - but ultimately useless - pieces of trivia about the movie.

 

1. Jennifer Garner took a break from the TV series 'Alias', for which she was best-known, to make '13 Going on 30'. It was her first starring role in a film.

2. Jenna turns 30 years old exactly 13 minutes into the film.

3. Young Jenna and young Matt were originally played by different characters but after test audiences reacted negatively towards them, the parts were re-cast and scenes re-shot.

4. Christa B. Allen, who played 13 year old Jenna, was such a dead-ringer for a young Jennifer Garner, that she also played the younger version of the actress in 'Ghosts of Girlfriends Past'.

 

5. When 13yo Jenna goes into the closet for "seven minutes of heaven", there are actual photos of Jennifer Garner as a kid on the back of the door.

6. The Six Chicks included Ashley Benson, who later starred in 'Pretty Little Liars', and Brie Larson, from 'Captain Marvel'.

7. Jennifer Garner, Mark Ruffalo, and Judy Greer were the studio's first choices to play Jenna, Matt, and Lucy. Gwyneth Paltrow, Hilary Swank, and Renée Zellweger were also considered for Jenna.

8. Mark Ruffalo's first scene was the "Thriller" sequence. He was terrified of doing it, but Jennifer Garner encouraged him with her "very infectious" enthusiasm.

 

9. If the cast wasn't sure if things were funny enough, they’d ask Judy Greer, because they all thought she was the funniest person on set.

10. Some of the scenes between Jennifer Garner and Mark Ruffalo were improvised.

11. Producers insisted on the slumber party scene, against the director's wishes. He felt it took away from Matt and Jenna’s romance - but later admitted it was one of the best scenes in the film.

 

12. '13 Going on 30' was a sleeper hit, grossed a surprising $96 million worldwide in the box office, and later earning nearly $60 million in DVD rentals.

13. The fashion magazine was initially named 'Sizzle' before the filmmakers settled on 'Poise'.