The Mega-Octopus Missile was a missile utilized by the SWAT Kats. A larger version of the ordinary Octopus Missile intended for use against monsters and other targets too big for the regular Octopus Missile, one was utilized against the tri-head monster at the museum, grabbing it and knocking it off of the roof. However the beast reverted back to its ordinary form (that of Katrina Moorkroft’s pet ferret) and escaped. The Mega-Octopus Missile, meanwhile, survived the ordeal intact and was presumably retrieved by the SWAT Kats.
The Mega-Octopus Missile was always intended to be used in the series. Model sheets depict one being used to capture one of the long-necked flying reptiles from The Pastmaster Always Rings Twice. However, Spider Missiles were used against those creatures in that episode. Succubus! would’ve been the first time the missile was actually used.