"Frog" is 'kaeru' in Japanese, written: カエルThe word FROG is not a Japanese word, so it wouldn't mean anything in Japanese.The Japanese word for Frog is カエル
Only in the Japanese version of the movies.
Kero,
at the pond
かえる の おうさま(kaeru no ousama) is "frog prince" in Japanese.
Yes they take out the heart when the frog is still alive.
Kaeru.
Only in the Japanese version of the movies.
Kuroi kaeru
The name "Keroro" comes from the Japanese impression of the sound a frog makes, which is "kerokero."
Jewel Beetle Jewelled Frog Beetle
That is hard to say, however frogs are generally appealed as "cute" in Japanese anime (just look at Japanese keychains) so that is probably why.