13 Actors You Forgot Guest Starred On Your Fave Shows

When you're a serious TV addict (whether you want to admit it or not), you start to realize that you basically know every single actor out there. No matter what kind of shows you're into, you tend to start recognizing the guest stars, and then all the faces start to kind of blur together after a while. Whether your absolute all-time favorite show is the 90s sitcom gem about the close group of Friends or you're a Gilmore Girl mega fan who is counting down the days until the Netflix revival, you probably have completely forgotten how many famous actors have been guest stars. It was usually way before they were famous, so looking back, it can be pretty funny and just plain fun to watch them. Here are 13 actors that you forgot guest starred on your favorite shows.

13 Julia Roberts (Friends)

Remember her character on Friends? She was pretty hard to forget but there are so many fabulous guest stars on this sitcom, it's okay if her episode slipped your mind. Julia played an old classmate of Chandler's who basically steals his underwear and clothes in order to get back at him for something that happened when they were kids. It was pretty hilarious and memorable, and it's always awesome to see Chandler in a sticky situation, as he's just pure comedy gold.

12 Jon Hamm (Gilmore Girls)

Yup, the handsome and dashing Mad Men favorite was even on the small town, mother/daughter fast-talking show. He went on a date with Lorelai in the fifth episode of season three and she basically hated him. Yeah, we know, how is it possible to hate Don Draper? Not sure. They meet at an auction that Emily forces Lorelai to go to, so it's no wonder Lorelai is so bored and not into things at all, considering her difficult relationship with her mom.

11 Ben Stiller (Friends)

Yup, Friends again. Ben Stiller was Rachel's absolutely nuts date. They called him "The Screamer" because, well, he would go into total fits and start freaking out about anything and everything. It was totally hilarious, of course. If you were watching this episode, "The One With The Screamer" at the time (1997 to be exact) you might not have thought it was a big deal, since of course he broke big with Zoolander in 2001. But now that you know how famous Ben Stiller has gotten, it's pretty fun to re-watch this episode.

10 Lauren Graham (Seinfeld And Caroline in the City)

The woman best known as Lorelai Gilmore (aka everyone's absolute fave TV mom) had a rough time breaking into the acting business. So way before she broke big with her role, she was a guest star on two old-school sitcoms. She played a character named Valerie in a season eight episode of Seinfeld and was part of a funny storyline about speed dial. She was also in five episodes of Caroline in the City and played a weird woman named Shelly who had a very weird accent.

9 Seth Rogen (Dawson's Creek)

You had no idea, right? This is one celeb cameo you probably can't believe that you forgot but it happens. Seth Rogen (aka part of the Judd Apatow crew) was actually on an episode of the 90s teen drama. He was in a sixth season episode and is basically a Judd Apatow character since he smokes a lot of pot and makes jokes while Joey and her college roomie Audrey and boyfriend Eddie go to L.A. Crazy, right?

8 Jane Lynch (Dawson's Creek)

You, of course, know Jane Lynch as the hilarious and super mean Sue on Glee. Before that, though, she was on Dawson's Creek… as Pacey's mom. Yup, actually. Bet you didn't remember that since we never really got to see Pacey's mom or his family very often (besides hearing that he was basically the black sheep of his family). Jane's character is also super religious, which is rare for the show, besides Jen's grandma of course.

7 Mae Whitman (Grey's Anatomy)

We're sensing a theme here… Mae Whitman, who is best known for playing Lauren Graham's other TV daughter Amber on the now cancelled (sadly) family drama Parenthood, was in an episode of the Shonda Rhimes hospital drama. She was a smart aleck teen which was not a stretch since of course that was what Amber was like.

6 Kyle Chandler (Grey's Anatomy)

Coach Taylor (your Texas TV crush) from Friday Night Lights had an amazing guest star role on Grey's -- probably the best guest role there ever was. Remember the bomb episode? Kyle's character is the leader of a bomb squad who helps Meredith when a patient comes into the hospital with, well, a bomb inside of him. Scary stuff and an absolutely incredible episode. Ah, the good old days of this doctor show…

5 Abigail Breslin (Grey's Anatomy)

Grey's again, but for a good reason: you adore Abigail Breslin, right? She used to be the most charming, adorable and wise-beyond-her-years child actor, and you first knew her in the horror movie Signs as the girl obsessed with water glasses. Hilarious. Today she's all grown up and wrote a sweet advice book This May Sound Crazy and is, of course, starring on the Ryan Murphy show Scream Queens. Before all that, though, she was on Grey's (the third episode of the third season, specifically) and charmed fans as a young girl who believed she was magical because she was never in pain if she got hurt.

4 Matthew Perry (Beverly Hills 90210)

Yup, Chandler was on the famous teen drama. He played a wealthy classmate of Brandon's who loved tennis but seemed pretty miserable. Of course Brandon, being the cheesy roving journalist he was (at least for the school newspaper), got super involved and tried to save the character. Oh, Brandon. Always so nosy and getting into someone else's business.

3 John Slattery (Desperate Housewives)

The Mad Men star (yup, another one) was a recurring guest star on the soapy suburban drama. You may not remember him and that's totally cool, because how crazy was this amazing and fun show? There were so many plot twists and turns that it's pretty much impossible to remember every single character and storyline. But John Slattery was Eva Longoria's second husband in the fourth season, and he was pretty evil -- but just as dapper as his Mad Men character, naturally.

2 Will Smith (Blossom)

Remember Blossom, the adorable 90s flowery sitcom? She grew up as the only female in her household and had a sweet, loveable musician dad and two goofy older brothers. She was super fashionable, too, and her best friend was named Six (the best name ever, really). But did you know that Will Smith was a guest star on an episode? Yes, really. Blossom and Six learned he was going to be nearby and so they completely freaked out and got totally excited.

1 Stockard Channing (The Good Wife)

The Grease star plays none other than Alicia's mother on the legal drama that is now in its seventh and final season. She's pretty hilarious and basically an alcoholic, so she brings a much-needed sense of comic relief to the sometimes serious show. She's featured on the show more in recent seasons but doesn't get a ton of screen time, so she's not as flashy as some of the show's other guest stars, like Michael J. Fox.