I found the complete episode script here: https://www.melissazone.com/sabrina/transcript.php?id=132 Josh- "It was unusual, but amazing. Just like the rest of the evening." The words Josh was saying here means that the Machu Picchu Civic Light Opera that Sabrina took him to see was something that he considered out of the ordinary compared to activities he has done on other dates he has been on with other people in the past. However, Josh still enjoyed his time with Sabrina. Josh-"You know, when I made that comment about the Machu Picchu Civic Light Opera, I didn’t actually know there was one." What Josh means here is that after Sabrina took him to see "an obscure documentary on North American Eskimos" (you can find this conversation mentioned earlier in the script), an activity he also considered to be out of the ordinary compared to activities he has done on previous dates with other people, he had asked her if they were going to see the Machu Picchu Civic Light Opera as a joke. This was a joke because Josh considered this to be an out of the ordinary activity that if it existed Sabrina would probably take him to see it because she has already taken him to see that unusual documentary. Josh thought he had made up the name of this opera company, but he did not know that this was in fact the name of an actual opera company, and Sabrina takes him to see it. Sabrina-"But how good were they? I mean nobody does ‘Fiddler’ like the Peruvians." When Sabrina says the above phrase in response to Josh. She understands that Josh made the Machu Picchu Civic Light Opera comment as a joke, and also agrees that it was a great performance. 'Fiddler' is the short way to refer to the famous musical 'Fiddler On The Roof'. Sabrina mentions the Peruvians because they are native to the land, Peru where Machu Picchu is located. There is laughter after Sabrina says her line because it is considered ironic that Peruvians would be able to perform an opera so well that is about Jews.

Thank you, I still don't understand why the laugh about the Opera of Machu Picchu