Over the course of its six-season run, 'Sex and the City' featured a vast amount of guest stars. Whether they played a love interest of Carrie or the girls, or a parody of themselves, the cameos made added a fun element to the already dynamic show.

Such appearances were made by singer Alanis Morissette, Spice Girl Geri Halliwell and supermodel Heidi Klum. Although Bradley Cooper and Matthew McConaughey are now A-list stars, they were much less well-known when they had guest stints on 'SATC.'

And as unexpected as the 'Sex and the City' plotlines were (Carrie getting trampled by a model, anyone?), sometimes the guest stars were even more unexpected! Check out our top picks of the most surprising cameos that you may have forgotten about below.

Geri Halliwell

You may recognize her as the Union Jack-wearing Spice Girl, but Geri Halliwell honed her acting chops in the sixth season of 'Sex and the City.' Ginger Spice played an acquaintance of Kim Cattrall's Samantha Jones. Geri's cameo was brief -- she appeared just long enough to taunt Samantha with her exclusive pool membership. Rough life, man.

Bradley Cooper

Long before his Oscar nominations, Bradley Cooper was just an almost-fling of Carrie Bradshaw. During the second-season episode, Sarah Jessica Parker's character suffered a major blow to her ego following an unflattering magazine cover. Carrie almost hooks up with Bradley's character to boost her self-esteem, but ultimately (and literally) walks away from the situation.

Matthew McConaughey

One of the series' most memorable cameos came from Matthew McConaughey, who played a parodied version of himself. During the season 3 episode, Matthew met with Carrie to discuss playing Mr. Big in a movie adaptation of her newspaper columns. Much to Carrie's horror, Matthew blames her for her failed relationship with Mr. Big. Despite her conflict with the now Oscar-winning actor, his ability to play up his persona makes this guest spot a true 'SATC' classic.

Eddie Cahill

You may recognize Eddie Cahill from when he played another younger man dating a cougar in 'Friends.' During his brief appearance in 'Sex and the City,' Eddie's Sean plays a bisexual man pushing Carrie out of her comfort zone. After attending a party in which she kisses another girl (read on for more about that), Carrie's relationship with Sean leaves her wondering if gender really exists.

Alanis Morissette

Remember when we mentioned that Carrie kissed a girl? Well, it happened to be songstress Alanis Morissette. During an ill-fated (depending on how you look at it) game of Spin the Bottle, the two women shared a brief lip-lock, making Alanis' cameo memorable in more ways than one.

David Duchovny

When Carrie meets up with her high school sweetheart in season six, their flame is suddenly rekindled. After the pair sleep together, her ex, played by David Duchovny, confesses that he's currently a patient in a mental facility. Carrie is OK with this until she visits and realizes the relationship may be more complex than she originally expected.

Heidi Klum

In season four of 'Sex and the City,' Carrie is enticed into appearing in a fashion show with actual models. One such model is a brunette Heidi Klum, who initially puts the writer at ease. After Carrie wipes out on the runway, however, Heidi gracefully stomps over her, making the journalist "fashion roadkill."

Vince Vaughn

The girls face a culture shock when they leave NYC for sunny L.A.. The health-obsessed city scorns smoking, but Carrie is quickly swept off her feet by Matt Damon's agent, played by Vince Vaughn. The comedic actor ultimately serves as a metaphor for the faux purses, lifestyles and attitudes that Carrie & Co. face while in California.

Jon Bon Jovi

In the wake of her post-Big breakup, Carrie's friends suggest that she see a therapist to sort through her issues. Naturally, Carrie picks up a fellow patient, played by rocker Jon Bon Jovi. She eventually sleeps with him only to realize that she's fulfilled her therapist's diagnosis that she picks the wrong men.

Sarah Michelle Gellar

The normally endearing and charming Sarah Michelle Gellar channeled a cutthroat Hollywood film executive in the third season of 'Sex and the City.' After obnoxiously making SJP guess who was interested in making her column into a film (answer: Matthew McConaughey), SMG proved that she can be as self-interested as she can be sweet.

Kat Dennings

You may know her as one half of 'Two Broke Girls,' but back in the day, Kat Dennings played a spoiled rich girl. The self-absorbed brat is a total departure from Kat's down-to-earth personality, which is one reason this cameo is so great. Seeing her butt heads with the fiesty Samantha Jones? Even better! (And it should be noted that even as a teen, Kat's hair game was on point.)