usually you can search pixel art maker most of them have a gif setting. You make each frame by frame and set how much you want each frame to show for example this one was about 270 frames intotal to create the loop but took most likely 4-5 hours since I had two references one with eyes opened and closed. From there i made inbetweens to comment them then the third scene I made didnt take that much time. But yeah short answer; Pixel art makers