The phrase "alien appearance" is correct and usable in written English.
It can be used to describe something or someone that looks foreign, unusual, or not of this world, often in a science fiction or metaphorical context.
Example: "The creature had an alien appearance, with its elongated limbs and luminescent skin."
Alternatives: "extraterrestrial look" or "unearthly appearance".
"This message comes to you today from an old country, France," the translator of Mr. de Villepin's remarks intoned through the large white earpieces that gave the roomful of more than 400 people a vaguely alien appearance.
First, I see his helmet, a meshed fencing mask with eyes drawn on to give it a smiley green alien appearance.
It gave them a striking, almost alien appearance.
Consequently, guesses about alien appearance usually proceed by attempting to forecast our own descendants.
Carroon's transformation was effected by makeup artist Phil Leakey, who worked in conjunction with cinematographer Walter J. Harvey to accentuate Wordsworth's naturally gaunt features to give him an alien appearance.
The first alien appearance in comics seems to be a strip about a Martian trying to make it on Earth called Mr. Skygack, from Mars, which ran in a Chicago paper in 1907.
They play Graeme Willy and Clive Gollings, two nerdish Englishmen, visiting the States for the first time to attend a convention of fellow sci-fi enthusiasts in San Diego and to travel by camper van around the west inspecting alleged sites of UFO and alien appearances.
The aliens' appearance is the cue for the film's one good line.
However, Nimoy then reappears among the crowd waiting for the alien's appearance (alongside the "Alien Dude: Need Two Tickets to Pearl Jam" poster-holder), leading to the immortal line to Bart: "Wherever there is a mystery and the unexplained, cosmic forces shall draw me near".
It's basically alien in appearance, and seems to have just enrolled into the trio of mummified alien bodies found on earth.
The INS had authority to place only those conditions on bond as are "related to obtaining an alien's appearance" at future hearings, the judge wrote.
