So I've spent most of the afternoon watching snippets of Friday Night Funkin' dev streams, and in one of them PhantomArcade mentioned how the characters were redesigned over time, but the game would keep the old sprites until the post-release since it would be already much more work to replace them with new ones.

If you compare Boyfriend's design on his sprites to the artwork that PA draws of him, you'll notice a few changes. His face is shaped differently, his shoelaces are simplified, and in some colored game sprites, the lower outline of his hair changes from black to dark cyan, in order for his eyes and eyebrows not to blend in with those. You can actually see those changes on the recent update, such as the new "yeah" pose in Week 2 and the results screen.

I always thought that BF looked off in the NIASB roster, so I've spent the evening tuning him out so he'd look like how he's drawn in the game.

Property of the Funkin' Crew.