Pipes

The pipes are, in the Mario universe, some pipes which often lead to various places, in which Mario can enter. SuperMarioGlitchy4's videos being mostly based on the video game Super Mario 64 on the Nintendo 64, several pipes then appear sometimes in his videos. They're usually inanimate objects, but in the blooper "Problematic Pipe Problems", they appear as living characters, and they have a chef called King Pipe.

Physical Description
The pipes exists in several colours, but the most common one is the green. The living pipes look exactly like the other ones, and have no face despite being living characters. However, one of them was seen wearing glasses.

Appearances in SuperMarioGlitchy4's videos
Pipes appeared in many bloopers of SMG4, but "Problematic Pipe Problems" is (actually) the only video in which they appear as living characters, and it's then their first and most prominent appearance.