~ちゃう (casual ~てしまう)

The casual contraction of ~てしまう to ~ちゃう (and ~でしまう to ~じゃう after voiced consonants). Conveys completion, finality, or regret, often with a casual or playful tone. 食べちゃった ('I ate it all up / I went and ate it'), 言っちゃった ('went and said it'), 忘れちゃった ('I went and forgot'). Carries the same regret/completion semantics as ~てしまう, just in informal register; common in spoken Japanese.