This is a scene from the Taxi episode "On the Job." Every year the show did a two-part episode consisting of little sketches for each of the cabbies; this was about the jobs the characters get when they're laid off from the cab company, and it was probably the best of those "sketchisodes." This sketch, with Jim as a door-to-door salesman, is one of those bits where it's not hard to guess what the punchline will be, but it's still incredibly funny because of the genius of Christopher Lloyd, plus the super-efficient direction of James Burrows back when he was still the best comedy director in the business.
The other thing that this scene illustrates is that even though the sitcom is generally considered a lesser form of TV comedy than sketch comedy (there's a reason Aaron Sorkin does a whole show about the power of sketch comedy to Change The World), there are actually some advantages that a good sitcom has. If this routine were done as a self-contained sketch with new characters -- and something like this routine probably had been done as a sketch not once but many times -- it would feel kind of bland. What makes it work better in Taxi is that it uses a character, Jim, who's built up a lot of audience goodwill in his two years on the show. Instead of a sketch about an idiot ruining a woman's carpet, which is what it would be on Saturday Night Live, it's a little story about a character we like; we know he's doing everything he can to succeed at something he doesn't really understand, and the scene becomes funnier and sharper because we're on his side. It's a better scenee because it's on a sitcom, not in spite of it.