God damnit, I was tricked! I performed a Seppuku and... and...! ;_;
The sepuku is sometimes needed to be able to continue the level in case one of your animals gets trapped, but usually those situations can be avoided. In SOME levels it can actually give you an advantage towards completing it with fewer total deaths, or just more easily in general, but this case is more common with custom levels than the prepackaged ones.
Currently wrapped up in: Half Life, Portal, and User Created Source Mods