Nobody’s mentioned Gort in The Day the Earth Stood Still? 
A seemingly Vulcan in the chair - ‘Damn…’
John Adams in 1776
When Kong busts open the big doors. Albeit, not his first appearance.
The buildup to Godzilla’s first appearance in the 2014 version was about as good as these things get.
I just introduced my son to the movie - my all-time favorite, and the first time he’d ever seen it. In all the (many) times I’d seen it before, however, I’d never noticed the date on the check: Dec. 2, 1941, just five days before the attack on Pearl Harbor. I checked on Wiki and learned that the Japanese fleet was already approaching Hawaii by then. A sobering thought.
Never mind.
You magnificent son of a bitch.
The viewscreen reveal of the Romulan Commander (Mark Lenard) in the Star Trek episode “Balance of Terror” as he turns to face the camera.
The arrival of Winston Wolf (Harvey Keitel) in Pulp Fiction, parodied by Wayne Knight in the “Muffin Tops” episode of Seinfeld.
I was just watching the commentary, and apparently they were not allowed to show rats in films in the early 30s. It was considered very bad taste and too shocking for audiences. Interestingly, the Spanish version had no compunctions against it. There are no armadillos nor any rats in the castle, but plenty of rats on the boat with a laughing Renfield surrounded by them.
So knock on wood.
(I can’t believe I missed that the first time…)
Made even more surprising by the reveal that he is also his Father (in Journey to Babel)!
And also secretly a Klingon (in ST:TMP!)
I agree with Ebert that the beginning of Le Samouraï is awesome.
Good one! 
Mark Lenard is the only actor I know of to play a Vulcan, and Romulan, a Klingon, and a gorilla.
It’s actually funnier in German:
“Haben Sie ein Pferd für mich?”
“Nein. Wir haben nur drei. Ein zu wenig.”
“Nein. Zwei zu viel.”