According to the UFO literature, UFO occupants come in different humanoid shapes and sizes. Regarding shape, the occupants have more or less the basic humanoid shape: two legs, two arms, a head, and bilateral symmetry. Regarding size, the UFO occupants are typically described as being small, ranging from roughly 1 to 1½ meters in height. But some witnesses have also reported encountering humanoids ranging in height between 5 and 13 feet tall.

From left to right: Reptilian Alien, Ancient Alien, Grey Alien,
Nordic Alien, Men in Black, Neonate Alien and Roswell Alien.

Here is what is known so far about these seven types of alien beings...

In some rare cases, information about alien physiology and anatomy was leaked by a few privileged insiders who revealed that autopsies had been performed on alleged alien lifeforms. One particular case was discussed on a 1988 television special entitled UFO COVER UP - LIVE! hosted by Mike Farrell, which is referred to as the Foreign Technology Division/Wright-Patterson AFB Alien Evidence.

Then, in 1995, the FOX Network aired a controversial film entitled Alien Autopsy: Fact or Fiction? hosted by Jonathan Frakes. It was subsequently aired twice more, each time showing more footage of the "autopsy" and crash debris. After having been around the media circuit for a while and the subject of controversy, the film was eventually discarded by most researchers when someone apparently claimed to have faked it.

Sources:

1979 MUFON UFO SYMPOSIUM PROCEEDINGS
O.V.N.I., DIMENSION AUTRE by Jacques Lob and Robert Gigi
OVNI by Yurko Bondarchuk
THE UFO ENCYCLOPEDIA by John Spencer
GLIMPSES OF OTHER REALITIES - VOLUME 1 by Linda Moulton Howe
Status Report II: New Sources, New Data by Leonard H. Stringfield
inexpliqué - Volumes 1 - 26 by Grolier Publishing
Falkville, Alabama Humanoid Photographs by Police Chief Jeff Greenshaw
http://www.ufoevidence.org/cases/case127.htm
http://www.ufo.se/ufofiles/english/issue_3/varginha.htm

UFOs or Unusual Floral Organs:

UFO During Floral Development
Avas Flowers Floral Company
Ratings and Reviews of Avas Flowers