What is fast happy when translated from English to Italian?

There isn't a single perfect translation for "fast happy" in Italian, as it depends heavily on the context. The phrase is somewhat unusual in English. Here are a few options, depending on the nuance you want to convey:

* If it means "quickly happy" (becoming happy quickly): `felice in fretta` or `rapidamente felice`

* If it means "easily made happy" (someone who is easily pleased): `facilmente felice`, `di facile compiacimento`

* If it means something is fast and brings happiness: This requires more context. For example, "a fast happy car ride" could be `un giro in macchina veloce e piacevole`.

To get the best translation, please provide more context about how "fast happy" is used in your sentence.