All-Nighter - S1-E9
Continuity mistake: When they are sitting around in sleeping bags, talking about hooking up in the store, part of the sleeping bag behind Glenn is straight up, forming a point. But in the next shot, the top part is folded over, so there's no point.
Chosen answer: He's just gained weight. It looks like he slowly started gaining more weight around 2006 or so. In "Kids in the Hall: Death Comes to Town" (2010) he's noticeably heavier than his younger days (he was on SNL 21 years ago). By the time he was in "Man Seeking Woman" he looks very similar to how he looks in "Superstore."
Bishop73