In Detective #263, Batman learns of an alien who crash-landed near a Mayan village some 100 months earlier:
The alien gave the tribe a few terrific alien tools including an anti-gravity sled, but crooks have stolen it from the tribe. Batman pledges to bring the alien tools back to the Mayans, but I should note that the ending of the story leaves that up in the air.
Status: True alien, appeared in the past and later left Earth. Green and human-sized. The concept of aliens leaving technology behind that is abused by local crooks is a very standard plot, so I'll give it only one Klaatu out of five.
Detective #270 features the Creature from Planet X:
Status: True alien, green and giant-sized. Two Klaatus awarded for this one; it's nice to see an alien who's enormous, but it's also the usual "convinced by crooks that acting crooked is normal on Earth," plot.
In Batman #124, the Seeds from Space appear, but once again the "alien" in the story is a robot:
Status: Not an alien, an alien robot.
In Batman #125, Batman becomes the King of the Planet Plaxius:
Status: Extraordinarily tricky. The planet is in another dimension, and the aliens do not appear alien; rather they just dress differently. Still, they do use space ships and so I'll call them true aliens, human-sized and caucasian in color. Four Klaatus for this unusual alien race.
In Batman #128; the dynamic duo get caught up in a dragnet for an interplanetary crook:
Status: True aliens; two different varieties; one orange-skinned and the other purple-red in color, with both human sized. Two Klaatus.
As you can see, the aliens were nowhere near as common in 1959 as they would become later:
Detective #263: True alien, green and human-sized
Detective #270: True alien, green and giant-sized
Batman #124: Not a true alien, robot
Batman #125: True aliens, caucasian and human-sized
Batman #128: True aliens (two separate species), orange and human-sized and purple-red and human sized.
Totals: Four stories involving true aliens, one story with an alien robot
1960:
Batman #130: Fake aliens
Batman #132: Fake aliens
Batman #136: True aliens, yellow and human-sized
Detective #277: True alien, orange and human-sized
Detective #279: Not a true alien, rather alien robot and alien beast
Detective #282: True aliens (two races): one orange and one green, both human-sized
Detective #283: True alien, white and human-sized
Overall for the year: Four stories with true aliens, one with an alien robot and an alien beast, and two stories with fake aliens.
1961:
Batman #137: True alien, white and human-sized and true aliens, yellow and human-sized (two separate stories).
Batman #140: Superman appearance; not counted in the tabulation, and true aliens, green and human-sized.
Batman #142: True alien, orange and human-sized.
Batman #143: Not a true alien, an alien beast.
Batman #144: True aliens, yellow and human-sized.
Detective #287: True aliens, one white and the other yellow, both slightly smaller than humans.
Detective #291: Not a true alien, an alien beast.
Detective #292: Superman cameo, not counted in the tabulation.
Detective #293: True aliens, pink and oversized.
Detective #295: True aliens, yellow and human-sized.
So in total we have 8 stories with true aliens (counting both stories in Batman #137), two stories with alien beasts and two Superman stories.
1962:
Detective #299: True aliens, several, green or white, human-sized.
Detective #303: Fake aliens.
Batman #148: True aliens, green and human-sized
Detective #305: True alien, orange and human-sized
Batman #152: Fake alien.
Three real aliens, two fake aliens.
1963-1964:
Batman #153: True aliens, green.
Batman #153: True aliens, multi-colored.
Batman #156: Fake alien (dream sequence)
Detective #320: No alien visible but implied.
Batman #160: Fake Alien
Two real aliens, two fake, one not seen.
