There is also an image of the small head on the original Cancer Masterforce toy (whos gallery can be seen here). The pic makes sure to show us the tech specs with the middle one being down meaning that the little head can actually be inserted into that slot.
Other things to note are the names used for these toys. "Shockwave" is used for both the Latin writting and the Japanese writing, rather than Laserwave, while "Cancer" is used for both. Fellow Seibertronian Sabrblade broke it down for us:
Sabrblade wrote:For the name "Shockwave", Takara always the Hasbro names in Latin script on the Legends packaging, while using the original Japanese Takara names in Katakana. But in this case, since the Katakana name is also written as "Shockwave" instead of "Laserwave" (along with several other Takara Shockwave toys of recent years using "Shockwave" instead "Laserwave"), that tells me that Takara must have lost the rights to the name "Laserwave" and are now using "Shockwave" as a substitute, with the MP being an exception to this since it seems Takara absolutely wanted to use "Laserwave" for that toy in some manner that they could (which make sense given how the MP line is their bread and butter celebrating the original cartoon with the authentic Japanese names), which resulted in their going with "Destron Laserwave" (essentially an equivalent of Hasbro using "Decepticon Shockwave") for the MP.
For the name "Cancer", however, with his name being written as such in both Katakana and Latin script, that further emphasizes how he's a completely separate character from Hasbro's original Squeezeplay/Crashbash character, and I'm all for their doing it since he very much is his own character (being an Earth human rather than a Cybertronian robot, for one).