An unlikely object is at the center of a How I Met Your Mother plot hole: Marshall and Lily’s toothbrush. Having been together since college, Marshall and Lily are the most solid couple on How I Met Your Mother. With such a long romantic history, Marshall and Lily are bound to be incredibly close and share more than just secrets.

Though Lily and Marshall break up when she accepts an art fellowship across the country and Lily disappears briefly in HIMYM season 4, Marshall and Lily are end goals. Marshall and Lily have fought for their relationship and to better themselves. However, their bathroom habits are questionable as Marshall and Lily’s toothbrush creates an unexpected HIMYM plot hole.

How I Met Your Mother's Toothbrush Story Makes No Sense

In How I Met Your Mother season 1 episode “Zip, Zip, Zip,” Marshall and Lily are seen in the bathroom, brushing their teeth simultaneously, proving the toothbrush story introduced later makes no sense. In How I Met Your Mother season 5 episode “Perfect Week,” Marshall and Lily reveal how they have been sharing a toothbrush for years. It is revealed that while living with Ted, the three shared the same toothbrush as Ted thought they kept their toothbrushes in the bedroom.

Marshall and Lily think a shared toothbrush is entirely normal, whereas everyone around them thinks it’s strange. They even scare off a new couple when they accidentally mention “our toothbrush.” However, after the reveal ing Ted’s toothbrush, Marshall and Lily appear visually disgusted, potentially implying that they each thought the lone toothbrush belonged to the other and not Ted. The shared toothbrush reveal directly contradicts their previous bathroom behavior.

Explaining Marshall & Lily's HIMYM Toothbrush Plot Hole

How I Met Your Mother’s shared toothbrush story may have a completely reasonable explanation. Considering the theory that Ted’s narration made Barney look bad intentionally, it’s entirely possible that Ted’s narration would purposely mislead his children into thinking Marshall and Lily had separate toothbrushes, so he could tell the real story later. It would make sense because, at that point in the story of events, Ted has no clue Marshall and Lily are sharing a toothbrush.

It's also years later that Ted is telling the story. So it would no longer be surprising that Marshall and Lily share a toothbrush. If he mentions the duo was brushing their teeth during his story, his kids will naturally assume it is with separate toothbrushes and not taking turns. How I Met Your Mother does not give a solid reason behind the toothbrush plot hole, but Marshall and Lily’s shared toothbrush is a strange habit that reiterates their close relationship.