This one is an oddity: a cover that was redrawn twice, for no immediately discernible reason.
The 1975 Danish first edition of La corne de rhinocéros (Spirou #6, “The Rhinoceros’ Horn”) features an original cover by a 17-year-old Peter Madsen, who as previously discussed was recruited by publisher Interpresse for the job. Compared to Franquin’s elegant and intriguing, but somewhat sedate original cover (below), it’s clear that the replacement achieves a couple of goals: it has more action and excitement, and it features Spirou and Fantasio within the main scene. Although the depiction of the heroes leaves something to be desired, the picture strikes me as relatively successful, and the choice to go with a cover like this is understandable. (Both these covers were used in Norway and Sweden as well.)
What’s really puzzling is that for the second printing in 1978, Interpresse replaced it with another one, also (by the looks of it) drawn by Peter Madsen, and nearly identical in subject matter and composition. However, on closer inspection it is clear that it has been entirely redrawn. Changing the rhino to be in full running charge adds energy to the scene, but other changes seem completely arbitrary (Spirou has lost his hat, and his jacket is open; Fantasio has been moved to the other side of the picture, and background details are different). Nor is there any appreciable improvement in how well the characters are drawn; in fact, Fantasio looks rather worse in this version.
The best explanation I can think of is that Interpresse had lost the print sheet for the first cover, and asked Madsen to recreate it, which he did somewhat approximately. Or perhaps he had created multiple alternative versions in the first place, and Interpresse for whatever reason changed their minds about which one they liked best. In any case, it gives us two different pseudo-Franquin covers to choose from, perhaps appropriate given that significant sections of the current version of the album were not drawn by Franquin. But that’s another story…