There are many different variants of the bat enemies: In Crash Bandicoot, they ca be found in several levels inside and outside the ruins. They are brown in color with pink fur inside their ears.
In Crash Bandicoot: The Wrath of Cortex, bats are purple in color, lighter colors on the wings, mouth and bellies, have yellow and red eyes and little white fangs poking from the upper jaw. They seem to lack feet.
In Crash Bandicoot Purple: Ripto's Rampage, the player can complete certain levels by riding on top of a big light gray bat. This look like a combination of the brown bat and the purple bat previously discussed.
In Crash Twinsanity, white bats can be found in snowy areas, while red bats can be seen flyinf around in the sewer areas.
In Crash Bandicoot, bats move in groups: a couple of bats can be seen hanging from walls, sporadically a row of bats can be seen flying from one bat to the other, leaving the screen afterward by going up. The two bats hanging from the wall can be spon away to stop the other bats from spawning and every single bat of the row is weak to a spin attack, although is pretty difficult to get them all with a single spin. In temple reuins levels the two bats on the wall are missing, and it's the only time the bats fly towards the camera.
In Crash Bandicoot: The Wrath of Cortex, bats fly around in circles, causing danger if Crash tries to jump in the air. They can be easily defeated by spinning them away at anytime. If Crash is hit by the wizard's magical energy in this level, then he will turn into a bat similar to the ones in the same level.
In Crash Bandicoot Purple: Ripto's Rampage, the player needs to ride a bat to get through certain levels. The bat is fully controllable and doesn't have a particular behaviour.
In Crash Twinsanity, bats strike by swooping down at Crash. Red bats are later seen in the sewer levels where they fly from side to side over pits, leading to an obstacle when crossing them. It was originally planned that they would appear in the level Jungle Bungle, in which they were going to come out of the caves and spread across the level, and in the level Cavern Catastrophe where they would have attacked Crash and Cortex if they stayed still for too long.
There is another unseen bat depicted in a green gem gallery in Crash Twinsanity, along with the white variant. This particular bat is purple and dark red in color and looks to be hanging upside down. It is currently unknown where it would have been encountered, however it likely would have appeared in the Cut Temple Level.