For all his work on TV and in movies acting with others, Conway was probably best known for his sketches with Harvey Corman. It wasn't just because they were so good together, but because it was difficult for Corman to keep a straight face, and much of the fun was seeing how long he could go before breaking.
Here's a sketch they did later in their career, live at some event. What stands out is how long both of them, but Conway in particular, are able to stretch out something as simple as buying a ticket, and keep it funny. What also stands out is the musicians -- who tend to be jaded, having seen it all -- behind them laughing, And as much as Korman is able to make it through the sketch in one piece, yes, he does fight to keep from breaking a few times. Without full success.
And okay, here's a bonus. It's Tim Conway and Harvey Korman's most-famous sketch, 'The Dentist' on The Carol Burnett Show. Famous (again) not just for being funny, but for Korman's eventual inability to keep from laughing at Conway and his struggles trying not to.