It's always challenging to come up with an iconic character design. No matter how skilled the artist you commissioned to generate a character design is at their craft, there are a host of elements within any character's aesthetic that will eventually have to be refined, and sometimes publically, in various subsequent drafts.
Compare any famous mascot or character's original design with their current incarnation, and the seemingly subtle differences between the iterations will be quite pronounced. One needs to look no further than nightmarish versions of the Simpson family that appeared on The Tracey Ullman Show to see how frequently characters are redesigned throughout the years.
The true test of how iconic a character's design is has nothing to do with their first appearance but rather the number of art styles they can exist in without losing appeal. In the video linked above, you can check out the YouTuber MillkunTV drawing Mario in a variety of different anime styles.