This film was originally intended to be part of a double feature with the movie version of the cartoon series "G.I. Joe" ("Action Force" outside the U.S.). In both cases the makers were granted permission to kill off the majority of the cast so that new characters (and therefore new toys) could be introduced to carry on the storyline. Transformers was the first to be released to a veritable onslaught of negative feedback (possibly due to the slight technicality that children don't like seeing their favourite characters die). This prompted a massive overhaul of the G.I. Joe movie with the result that in the finished film, many of that series' main cast sustain the same level of injuries that Optimus Prime and others suffer, only they just lapse into comas.
Ultra Magnus was suppose to die in a different way at first. The sweeps fired long laser beams that looped round him, and then they all flew off in different directions, ripping Ultra Magnus apart. Censors forced the artists to change it since it was to violent for a kids movie. However, you can still see the Sweeps fire the long laser beams, but when the shot changes lots of little laser blasts his Ultra Magnus.
A trailer for the Japanese movie has been found that has a lot of unused footage on it, and can be downloaded off www.seibertron.com The unused footage includes a lot of extra animation for the part where Unicron eats his first planet, Ultra Magnus in different colours, a shot of Autobot City's defences firing at the Decepticons, a shot of the Decepticons avoiding fire (but Skywarp takes a hit), a very different looking Autobot city, unused shuttle footage (with Arcee and Daniel on the same ship as Hot Rod, Kup and the Dinobots) etc. It is believed that this was originally "test" animation to see how the movie could look. Use the link and scroll down, then click on the "TF Movie Promo" http://seibertron.com/media/commercials/?path=/Transformers%20G1.
One scene that is in the script and almost made it into the movie involves Dirge trying to tackle Optimus Prime as he talks to Megatron, but Prime manages to slam him into the ground. In the actual film, this deleted part of the scene was suppose to happen just after Megatron says "Why throw away your life so recklessly?" This is why Optimus Prime looks like he is getting up from a crouched position.
The movie marks the first ever appearances of Blaster's cassette transformers. However, originally they were suppose to be different designs. There was only 1 robot, called Bolts. The other three with animals. Cubbie was a lion, Stinger a scorpion, and Stripes a tiger. They were changed later to two robots and two animals, a rhino and a lion.