I saw this in my YouTube subscriptions. He made three appearances on Hey, Landlord in 1966 and 1967. He was credited as Big Guy in this 1967 episode. Richard Dreyfuss was also in it.

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Garry Marshall's first solo effort was this sitcom starring WILL HUTCHINS, SANDY BARON and MICHAEL CONSTANTINE. ROB REINER was in 3 episodes. This one is titled "TESTING, ONE, TWO" and not even listed in Rob's imdb. Rob was about 18 or 19 here. RIP, Rob. You are missed.

HEY LANDLORD with teenage ROB REINER, 1966 NBC sitcom (https://www.youtube.com/watch?v=XgqHZO0xIco)

XgqHZO0xIco

Oh wow , I never even heard of this show!

Whats the landlords name on that show Todd do ya know buddy??

This one we might be able to chalk up to the Carl Reiner/Garry Marshall connection.