After Dorothy left Oz and returned home to Kansas, the Cowardly Lion had been turned into a stone statue by the Nome King, but thankfully Dorothy defeats the Nome King and restores the Cowardly Lion to his regular form. Among many other Ozians, he celebrates Dorothy's victory and witnesses the return of Oz's true ruler Ozma. He also says goodbye to Dorothy as she hugs him when she departs, knowing she will return to Oz another time.
The Cowardly Lion appears in the prequel as a cameo, attacking Oscar and Theodora as he was hunting Finley when he is trapped in weeds. Oz saves him by performing "magic" (a puff of red smoke) in the animal's face. He becomes scared and runs away. In this version, the Lion does not speak, but he does keep his personality. His existence is alluded to when Oscar calls him a coward as he fled.
In the episode "Wizard of Odd", the Cowardly Lion does not actually appear, but Buford Van Stomm portrays a similar character, a lion/tiger/bear cub. He consistently states that he does not want anything. At the end, Phineas and Ferb give him a sandwich.