Uh, sorry, saw your question first today... I made them with Krita, a free drawing program. You can use it to animate, too, really good. For the critters I often use photos as a basis, cut them apart in Krita and then paint on them using a drawing tablet. You really need a drawing tablet if you want to make more advanced animations and backgrounds, too hard with only a mouse.
Btw, sad to hear you abandoned your Drake Live game!