In one shot, Skyfire is drawn so huge that he can only peek inside the Decepticon lair. It is true that he is taller than most other robots, but he isn't that big as this shot would suggest.
Skyfire's ensign changes seemingly randomly. Sometimes parts of it are missing, sometimes it isn't drawn at all or colored with the wrong color. He is even shown wearing a badly drawn ensign before he receives one.
Prime's trailer disappears and reappears from scene to scene when they go into the Decepticons' base.
In one shot, we can see Gears sitting in front of a small computer screen. When we cut to a closeup shot, the screen is suddenly huge.
In one shot, Optimus is colored dark blue rather than red.
One shot has the snow "falling" upwards.
When Prime spins the green crystal spike around, it isn't colored in, and we only see its white outer lines.
When the Decepticons are ordered to battle, Starscream, Thundercracker & Skywarp transform into their plane modes, the entire nosecone is colored yellow. Usually only the cockpit is colored yellow.
During a flashback set 4 million years before-hand, Starscream recalls how he and Skyfire previously visited Earth. In the flashback, Starscream is shown in his current form as an F-16 fighter when he should have been portrayed as a Cybertronian jet from before the Transformers crash-landed on Earth.
In a flashback, Starscream is shown flying in his Earth form, an F-15 Eagle. The scene takes place millions of years ago, so him having an Earth jet as a vehicle mode would be impossible.
When the Autobots decide to investigate the mysterious readings in the Arctic they transform and drive from their base (widely accepted to be in Oregon) to above the Arctic Circle within an incredibly short amount of time. A drive of that nature would take several days and also cross significant terrain where there are no roads.
When Megatron orders Skyfire to kill Optimus Prime, Prime is mouthing his words.
When Skyfire awakens, Starscream's mouth is moving, but no words are coming out of it.
When Skyfire is buried under ice, his Autobot fellows mourn over his apparent demise, then the episode ends. Why don't they dig him up? They do it a couple of episodes later anyway, but it is never explained why they left him buried in this episode, especially given what a useful ally he is.