Goofs

In numerous scenes the characters can be seen surviving in space WITHOUT taking the oxygen pills it is often established they need to survive there.

Footage was reused constantly on the show, which often created continuity problems. For instance, whenever another one of the Fireball XL craft took off, they used the same footage used for Fireball XL5 - and you can clearly see the XL5 markings on the craft. Additionally, often when approaching alien worlds, the same "world approach" footage is used. The problem is that the footage is of EARTH (identifiable by the (rather obvious) continent of South America.)

During Fireball's launch sequence, seen in every episode, the smoke from the rockets casts a shadow on the painted backdrop.