The Unnamed Blue Android is a prototype version of Future Android 17 that is shown in flashbacks of both episodes Mystery Revealed and Double Trouble for Goku. Also, he is the villain of the ova The World of Dragon Ball Z since he is shown at the very end.
However, unlike Android 17 or Future Android 17, this android rather mangles his creator than kills it, and is probably how Dr. Gero became Android 20 due to the fact that underneath of his hat is a cybernetic brain which was were it first attacked him from when it escaped the vault it was in.
- Future Android 17 first cameos in "Mystery Revealed", depicted as a large muscular blue Android with red eyes, he kills Gero by crushing his body with a punch. This cameo is later shown again in "Double Trouble for Goku".