Astroquarium

When Astroquarium enters the battlefield, you may put an art sticker on it.
{1}, {T}: Until end of turn, target creature becomes a blue Shark with base power and toughness 4/4. If the cracks in Astroquarium's art are completely covered, that creature becomes a blue Octopus with base power and toughness 8/8 instead. Activate only as a sorcery.