This is probably my first article talking about two obscure but appealingly quirky bands which sang the same quirky song. First off, let's get into Juicy Fruits. Starting off as a rock band with some techno kayo stylings called Haruo Chikada & BEEF in 1979, a year later, Chikada（近田春夫） left and the band changed names (and food groups, apparently) and became Juicy Fruits in 1980.
Juicy Fruits debuted with what would probably be known as an earworm now with "Jenny wa Gokigen Naname"(Jenny in a Bad Mood). Written by the band bassist, Yuji Okiyama（沖山優司）, and composed by the departed Chikada for release in June 1980, the lead singer and guitarist, Atsuko Okuno（奥野敦子）, sings the song in a chirpy falsetto. The lyrics talk about the difficult title character getting herself into a lather about a boyfriend possibly straying far afield.
One of those bands which covered "Jenny" was hi-posi. I vaguely remember seeing a video of this duo on some show with vocal Miho Moribayashi（もりばやしみほ） as the camera jerked around strangely while the whole video looked very blurry. Moribayashi was singing in this soft whispery voice and everything led to this rather non-mainstream feeling coming through the screen.
hi-posi（ハイポジ） was formed in 1988 with Moribayashi, Kenji Kondo（近藤研二）, Naomi Araki（あらきなおみ） and Yu Yamaguchi（山口優）. In 1991, they made their major debut but Araki and Yamaguchi left a few years later. The band was a part of Shibuya-kei with their own techno stylings., and in 2000, Moribayashi brought her own whispery vocals to bear through a cover of "Jenny", some 30 years after its debut as the band's 12th single. There was a rather odd video to it but I can't seem to find it on YouTube at this time.
After Kondo left in 2000, Moribayashi was left all by herself but decided to create the first Terran interspecies band by having her Golden Retriever, Mizette, join. Then to further add to the canine content, Mizette's daughter, Mir, came aboard in 2003.
Anyways, some of the other artists who have covered "Jenny" are a couple of members from Morning Musume, Perfume and GO!GO!7188.