I think it makes the sketch 100x more hilarious when the cast can't hold it together. I love that they can make each other laugh.
  1. Rachel Dratch & Cast in Debbie Downer
    The entire cast slowly starts to laugh and then by the end pretty much none of them can keep it together, Jimmy Fallon is shoving waffles in his face to cope. The best part is when she says "We may never know how many people perished" and then tries to do the Debbie Downer face and just loses it. This is probably my favourite sketch of all time. http://youtu.be/TfE93xON8jk
  2. David Spade and Christina Applegate in Down by The River(Matt Foley)
    The best part is that Chris Farley is so in character and is going all out, while David Spade and Christina Applegate are struggling to keep it together when he's yelling: "You're going to be doing a lot of doobie rolling when you're living in a van down by the river!" http://youtu.be/Xv2VIEY9-A8
  3. Bill Hader as Stefon (Halloween)
    This one is pretty famous but it's just too funny not to put on. John Mulaney changed the cue card and put in an inside joke between the two of them and the look of realization upon his face and then him just losing it is priceless. http://youtu.be/KBCUz0Ugdzc
  4. Will Ferrel/Rachel Dratch in Luvahs in the Hot Tub
    Will Ferrel and Rachel Dratch exchange a look after he says in his priceless voice: "somewhere in the distance we heard the pounding of Native drums" and then they both can't stop laughing, it's too funny. http://youtu.be/gqeQLV04kwU
  5. Kristen Wiig, Bill Hader, and Fred Armisen in The Californians
    THE ENTIRE SKETCH. None if them can keep a straight face doing those voices. "Uuhhhwhuuutareyouuuu doing heeere?" I love this sketch SO much. http://youtu.be/Tt-tG6ufH90
  6. Ryan Gosling, Kate McKinnon, et al in "Close Encounter"
    Recent sketch featuring Ryan Gosling, Kate McKinnon, & Cecily Strong being interviewed by Aidy Bryant and Bobby Moynihan at the Pentagon regarding being the first humans abducted by aliens. While Ryan & Cecily describe transcending experiences, Kate's experience ranges from peeing in a tin bowl to having the aliens feel her up. Her lines are so obscure but are delivered with such certainty, everyone ends up breaking character and laughing by the end: https://m.youtube.com/watch?v=PfPdYYsEfAE
    Suggested by @bwyatt
  7. Jason Sudeikis, Bill Hader, Kenan Thompson, Andy Samberg and Lindsey Lohan in "Scared Straight"
    They crack up towards the end and no one can keep it together.
    Suggested by @michellejennifer
  8. Jimmy Fallon in the Cowbell sketch
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    Suggested by @joemurphy
  9. Jeffrey's
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    Will Ferrell, Jimmy Fallon, and Sean Hayes. Jimmy was basically laughing before the scene even started.
    Suggested by @rulesofjinx