You're both right! The robot the rocket was designed after was Robby from Forbidden Planet, and the regular cast member robot from LIS, "Robot", was not the same. HOWever... the Robby costume did appear in at least one LIS episode as an evil antagonist! (I watched way too much TV as a kid...)

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John Lance Ladd
Yoyodyne Propulsion Systems
Grovers Mill, NJ
Established 1938
lladd.netau.net