Tobias, the hawk Nothlit.
Nothlit is a word in the Andalite language that describes one who has passed the two-hour morph time limit, becoming trapped in their current form. It is normally impossible to regain morphing ability afterwards. Two exceptions to this are Tobias and Elfangor, both regaining their forms with the Ellimist's aid. A third was David, given a second chance by the Ellimist's counterpart, Crayak. A fourth is Cassie, who's morphing ability was "jump-started" by the metamorphosis from caterpillar to butterfly, the naturally-occurring morphing 'resetting' the morphing clock. Nothlits who become so by choice are often shunned by Andalite society, accidental nothlits to a lesser degree. The Animorphs at several times have avoided becoming nothlits, but Tobias failed, starting in just the first book, The Invasion.
Known Nothlits
While evading the Yeerks, Tobias became trapped in the form of a red-tailed hawk. He was able to regain his ability to morph in Book #13: The Change, but only regained his human form by being briefly sent back in time to acquire his own past self, rather than regaining his human body as his natural appearance.
In an alternate timeline, Elfangor volutarily became a human Nothlit, choosing a life on Earth, under the name Alan Fangor, and being married to Loren. The Ellimist reversed time to return him to his Andalite body, erasing most traces of his life as a human. All of this took place in The Andalite Chronicles.
While on a secret mission to the Taxxon homeworld, Arbron became a Taxxon Nothlit while evading the Yeerks. He would go on to become a hero among the Taxxons.
A Yeerk who longed for peace, Aftran was granted morphing ability by the Animorphs and became a humpback whale. All of this took place in Book #29: The Sickness.
In an effort to prevent David from exposing their secrets, the Animorphs executed a plan to trap him in the body of a white rat. He was later restored by Crayak, and his fate remains unknown.
Aldrea became a Hork-Bajir nothlit, living out the rest of her life with Dak Hamee.
Taxxon Rebels
The Taxxons who served under Arbron were granted morphing ability by the Animorphs, becoming anaconda nothlits. This stemmed from the desire to end their hunger, while retaining a similar form.
Cassie became a caterpillar nothlit, however her natural metamorphosis into a butterfly effectively reset the morph time limit, allowing her to become human again. All of this took place in Book #19: The Departure.
Menderash
Menderash became a human nothlit in The Beginning, so that the Kelbrids would not see an Andalite on board.
You
In Alternamorphs 2, The Next Passage, in one of the "death" endings, the Animorphs nothlit You as a fly, due to you killing Cassie.
Trivia
- In the TV Series, Ax pronounces the word nothlit as "not-lith" however, this could be because his voice is echoey and due to Jake speaking straight after, making it sound off.
- Applegate has said the word is almost an anagram of "Hilton."