What is the name of this Macromedia Shockwave game with a small plumber unclogging pipes from the inside?
Solution 1:
The game is called Puny Plumber.
I did a Google Image Search for your screenshot, which found me the website of its developer, Pizmo Games. Their copy of the screenshot is called "punyplumber2.gif".
Searching "Puny Plumber" will find you various Flash/Shockwave game sites that claim to have the game, although I wasn't able to run it. Here's an example: https://www.gameitnow.com/Puny-Plumber-online.