Vegeta is one of the central characters in Dragon Ball, the long running Japanese anime and manga series about powerful fighters, rivalries and transformations. The word iinaa is a common Japanese expression for admiring something and wishing it were yours, which fits Vegeta's proud but competitive personality perfectly. Short voice clips like this one circulate on soundboards and in short form edits because they carry a whole reaction in under a second. Fans reuse it whenever a character, player or creator sees something impressive and cannot hide their envy.