Ukraine was first mentioned in Nuclear Power, where it was revealed that he was the owner of several mutants (a result of the Chernobyl disaster in 1986) and that Sweden was looking after them. However, his first actual appearance was in Cold but heating up, where he was being harassed by Russia.
Ukraine looks similar to Azerbaijan, though Ukraine has appeared in 5 comics to Azerbaijan's single appearance. In Surprise Party Ukraine has a mustache.