I ask this cause they all look and they’re both equally different and equally the same at once somehow.
They’re all lava monsters who try to attack the player by leaping out of the lava.
In his original artwork, and in the cartoon, Iggy’s design was more similar to Lemmy, him being short and having a green shell, and rainbow coloured mohawk, it was pretty clear that these two were related.
However in recent years, these two have taken on a much different designs, Iggy still has his green shell, but he’s much taller now, and his hair is green and plant like, and Lemmy still has his short stature and rainbow mohawk, but his shell colour was changed to orange.
So it’s debatable whether these two are still canonically related or not.