It's always funny when the actors of a show get their real-life partners to join them on set, and this was definitely the case when Mila Kunis (as Vivian) randomly showed up at the beach house.
Of course, there were some jokes by Walden (Ashton Kutcher) about marrying her (which he does in the real world), and any fan of this pair would definitely find this utterly hilarious.
Miley Cyrus was Hannah Montana until 2011, and she broke out into adulthood and more mature roles soon after, and that included playing the eccentric, loud, and bubbly Missy on this sitcom.
She awkwardly dates Jake before she flees the series, but each scene with this talented gal is iconic. She never really stops talking, and it's kind of hard not to love Miley Cyrus in this small role.
For all fans of The Breakfast Club, it was a really exciting moment to see alum Judd Nelson appear on the show, although briefly.
Alan, of course, is terrified of him, and it makes for a pretty hysterical scene in the coffee shop. Judd Nelson's flair in this role makes it all the more hilarious.
If it wasn't weird enough that Charlie Harper is killed off, it's even weirder that Kathy Bates comes back as his ghost. Fans will remember the ninth season where Alan is in the hospital after a heart attack.
Naturally, why wouldn't Kathy Bates appear in a bowling shirt with a cigar? It's totally confusing, cringey, and also totally funny.
Like Miley Cyrus, fans will also remember Hilary Duff from the Disney Channel. When she appeared as a wild and drunk date on this show with Walden, it was pretty hysterical for anyone who knew her as Lizzie McGuire.
She gives Walden a pretty difficult time, and its certainly one cameo that's hard to forget - and also pretty hard not to have a good laugh at.
This show is surprisingly great at getting celebrity appearances from people who aren't actors, and that includes roping Brad Paisley into the mix. When Alan is getting married to Gretchen (Kimberly Williams-Paisley), a wrench is thrown in when Brad Paisley - her ex-husband, Derek - appears.
These two are actually married in real life, and that only makes this appearance even more memorable - and of course, worthy of a lot of laughs.
Any cameo on a sitcom with a fellow seasoned sitcom star are bound to be some of the best.
His character gives everyone some serious George Constanza vibes, but somehow even a bit more weird. He and Jon Cryer together was a golden moment for this series, and made for a perfect guest appearance.
During the first episode of season 7, Charlie is at the recording studio with Mia, and is having a tough time being involved with since he's in love with Chelsea.
It's a very, very brief scene, but the rock star comes out of the bathroom holding his guitar - immediately becoming iconic. There aren't many cameos that get better than this one, and this legend deserves so much love.
Fernando the handyman might be one of the best and funniest supporting characters to hit this series. In season 4, fans get to fall in love with Enrique Iglesias even more. And yes, he sings.
They totally exploit his singing and his charming good looks, and it's funnier with each passing second. He certainly gives Charlie Harper a run for his money, and it is a memorable celebrity appearance.
Fans will never know how the producers of this show convinced Jeff Probst to stand nude holding nothing but a pizza box. But in season 11, the Survivor host did exactly that, and had a cameo as himself.
It's both totally shocking and hysterical, and is one celebrity appearance that will probably never fail to make fans laugh. Probst will never live this one down, but it honestly just makes him even cooler.
