It finally occurred to me why the newest Optimus Prime for Transformers: Dark of the Moon has a butterfly mode.
(Check out this link if you need photographic reference
http://powet.tv/powetblog/2011/02/10/toy-fair-2011-pre-toy-fair-reveals-for-hasbros-transformers/ )
Optimus Prime has gotten into the habit of dying and then coming back to life shortly thereafter over the years. He did it in several comics, the animated movie/season 3, The Revenge of the Fallen. One of the bright sides to being a robot is that resurrection is kind of expected to some degree.
In the anime/manga Excel Saga there is a character called Hyatt whose constantly coughs up blood and dies, only to come back to life shortly thereafter. She and her senior, the titular Excel, work for an organization trying to take over the world, and as such often go undercover and use pseudonyms. One such pseudonym for Hyatt is Convoy Butterfly.
In Japan, the original Optimus Prime is called Convoy.
So Optimus prime having a Butterfly mode is a reference to Excel Saga.
Even if it isn't intentional, it sure as heck is appropriate.