Pokemon Zukans are a type of figure named after the Japanese word for Pokedex/encyclopedia. These figures are generally made 1/40th scale of their Pokedex height entries, and are featured on simple round or oval bases, and also usually have evolution lines featured together. These figures were originally only available in Gashapon machines in Japan beginning in 2003, but were also recently made available in parts of Europe. Some Zukan sets have become exceedingly rare and expensive collector’s items, whereas more recent sets are rather easy to find for affordable prices.
Certain Pokemon break the 1/40th scale rule, because their size would have been too large to fit in the capsules for gachapon machines. Pokemon such as Dailga, Palkia, Giratina, Kyogre, Groudon, and others have been made in 1/50th scale rather than the typical 1/40th. Steelix and Onix have yet to receive Zukans, possibly because they are the second and third largest Pokemon and would be difficult to create scaled figures for. All other Pokemon from Generations 1-4 currently have zukans, while Generation 5 has about half and Generation 6 is currently getting more Zukans produced.
So what about the largest Pokemon, Wailord? Wailord, as well as Ho-Oh and Lugia, were given away as lottery prizes. The lotteries involved collecting certain tokens from the gachapon machines, and then mailing all of the required tokens in to be entered into the raffle. There are an estimated 1,000 Wailords, and 1,000 Ho-Oh + Lugia sets ever made and given out. I was lucky enough to have a Lugia and Ho-Oh set to take pictures of for this site, and both will soon be in new homes with dedicated collectors.