Originally from Hiroto Nakadai's world, Hiccup gets his name from the hiccup-like sound it makes when it is not petted: "Hic"
In the beginning, Kriss S. Sison (the artist) had no idea where to go with Hiccup's design. Originally Hiccup was designed to be much more serious, Kriss S. Sison designs went from rodent to alien blob, to cigar-smoking rabbit. The writer suggested for Hiccup to have a spider-like appearance the artist went from there and came up with what we see now.
Ikuko and Hiccup Meet for the First Time
When first introduced Hiccup frightened Ikuko, shortly after she warmed up to him and they both became heavily attached. When traveling to the Alternate School reality Alvin took Hiroto's pack inside the vents so he would have a place to put the Himmelskarte when he had found it. Because there was a guard there Alvin was stuck and knew not what to do to retrieve the device. Hiccup energetically jumped out of the bag and attracted the guard to follow it, giving Alvin the opportunity to retrieve the device. When the group was escaping from Sturch's army into another dimension Hiccup appeared again and went through the portal before the rest of the group.