1987- forever
“some people never change.  some do…" 
also more than you ever needed / wanted to know about animorphs from the animorphs wikipedia, btw:

To develop the characters for Animorphs, Applegate would go through teenage magazines such as YM and Seventeen (both of which are referenced in the books when describingRachel), cutting out pictures and piecing them together to get an idea of what sort of kids the Animorphs would look like. Applegate stated in an interview online [6] that many of the names for her alien creatures, races, and locations are actually scrambled names of local street signs or companies that she happens to notice. For instance, the word nothlit was derived from the hotel name Hilton. According to the Anibase, Applegate did not make up the titles for the Animorphs books: it was up to the Scholastic editors to create the titles for the books based on the outlines provided by the author, having to select a word that not only fit the book’s storyline, but sounded good with the characteristic “The” preface. One of the author’s favorite books, The Lord of the Rings, lent several words and images to Animorphs: the elvish word for Orc, “yrch”, became Yeerk; the flaming red Eye of Sauron inspired the Crayak, and Ax’s middle name, “Esgarrouth”, is based on a town in the books called Esgaroth. The human name of Ax’s brother, Elfangor, is Alan Fangor and his last name is in reference to the Fangor region or Fangorn Forest. Also there was a minor reference to Gondor, in the form of a fictional company named “Gondor Industries” in the 14th book. (It may also be significant that Visser Three's host is named Alloran, a rough homonym of Gandalf's Valinorean name “Olórin”, and that one of the minor alien races is called “the Five”, which is also a term used in The Lord of the Rings for the Istari.) Applegate’s writing was inspired by her family. All books after The Unknown were dedicated to Applegate’s son, Jake, as well as her husband and co-writer, Michael. Her son was born premature in 1997, and she worked on the Animorphs series at night, in the lobby of the hospital where he was in Neonatal Intensive Care (NIC).

some people never change.  some do…

also more than you ever needed / wanted to know about animorphs from the animorphs wikipedia, btw:

To develop the characters for Animorphs, Applegate would go through teenage magazines such as YM and Seventeen (both of which are referenced in the books when describingRachel), cutting out pictures and piecing them together to get an idea of what sort of kids the Animorphs would look like. Applegate stated in an interview online [6] that many of the names for her alien creatures, races, and locations are actually scrambled names of local street signs or companies that she happens to notice. For instance, the word nothlit was derived from the hotel name Hilton. According to the Anibase, Applegate did not make up the titles for the Animorphs books: it was up to the Scholastic editors to create the titles for the books based on the outlines provided by the author, having to select a word that not only fit the book’s storyline, but sounded good with the characteristic “The” preface. One of the author’s favorite books, The Lord of the Rings, lent several words and images to Animorphs: the elvish word for Orc, “yrch”, became Yeerk; the flaming red Eye of Sauron inspired the Crayak, and Ax’s middle name, “Esgarrouth”, is based on a town in the books called Esgaroth. The human name of Ax’s brother, Elfangor, is Alan Fangor and his last name is in reference to the Fangor region or Fangorn Forest. Also there was a minor reference to Gondor, in the form of a fictional company named “Gondor Industries” in the 14th book. (It may also be significant that Visser Three's host is named Alloran, a rough homonym of Gandalf's Valinorean name “Olórin”, and that one of the minor alien races is called “the Five”, which is also a term used in The Lord of the Rings for the Istari.) Applegate’s writing was inspired by her family. All books after The Unknown were dedicated to Applegate’s son, Jake, as well as her husband and co-writer, Michael. Her son was born premature in 1997, and she worked on the Animorphs series at night, in the lobby of the hospital where he was in Neonatal Intensive Care (NIC).