Oh yeah, for those who don't understand, Goldorak is the French name for Grendizer.
I'm glad that even the artist thought of that.
It gets even better! If you treat the image parent as part of one whole gag, it highlight the differences of status of Mazinger and Grendizer in Japanese and French anime fandom. Where in Japan, Mazinger is treated as the prime Go Nagai mecha anime and Grendizer is seen as "just" a spin-off. In France, it IS the anime that forever shaped French anime fandom, whereas Mazinger came much later in the channel M6, programed with Space Sherif Shaider and faced misunderstanding from French who only found out later that it is Mazinger that was the parent series of Grendizer.