Originally Posted by Deep thought

Here's several reasons why Goku dodged the disc:

1. Akira wasn't really thinking about power levels when he drew those two frames.

2. It would be the stupidest ending ever if the disc hit.

3. Some Ki attacks are slower than the people who use them.

4. Freeza yelled prior to firing the attack, causing Goku to be alert.

5. Freeza somewhat missed.

6. Freeza's power was decreasing steadily.

7. Freeza's discs aren't that steady.