SpongeBob is an optimistic and energetic character, but also very naive.

海绵宝宝拥有开朗的性格，是个乐天派，但同时也有些幼稚。

youdao

"This is not some naive, optimistic young man who has inherited a fortune and is about to blow it on some fantasy project on the north coast, " Mr Shaw said.

BBC: Northern Ireland

It would be naive to be optimistic after all that has occurred but there is cause for less pessimism.

CNN: Highlights from the world's press