Glenn is a Bad Place torturer and resident of Neighborhood 12358W. His first appearance was in Chapter 3. He made a memorable appearance in Chapter 4, when he attended the opening of The Good Plates and fell into the sinkhole which opened up in response to Eleanor's actions on the night.
In Chapter 5, "Glenn Martrempf" (who presumably is the same person) is shown to be the only resident rated lower than Tahani in the neighborhood point ranking.
In Chapter 13, he was one of the immortal beings in attendance when Michael pitched his "Good Place" idea to Shawn and the other archtiects, suggesting he may have a more important role in the Neighborhood than has yet been shown.
In Chapter 16, he was Eleanor's "soulmate" in one of Michael's many attempts at running his "Good Place" experiment.