Knuckles in Sonic 2: special stage sprites

Just as a quick aside: much like his running animation in Sonic 3, Knuckles' Sonic 2 special stage sprites were created by recoloring Sonic's sprites, then pasting a Knuckles head on top. More specifically, the head from his Sonic 3 special stage sprites, which is why the perspective looks a bit off.

The finalized sprite notoriously gives Knuckles tan arms, but don't be fooled into thinking this is noteworthy. Everybody has tan arms in the Sonic 2 special stage!

Similarly, Knuckles' appearance in the Sonic 2 title screen is based off of his 3D render from the Sonic & Knuckles title:

Note the incorrect transparency on the left fist in both games. Interestingly, the Sonic 2 title screen has more frames of animation than Sonic & Knuckles. I wonder if they were made specifically for Knuckles in Sonic 2, or are they evidence of a longer, scrapped Sonic & Knuckles title animation?