First cap is from EP243 - Same Old Song and Dance: Jigglypuff is rummaging through Misty’s bag and finds the handkerchief she then gives Ash in Gotta Catch Ya Later, exactly 30 episodes later. The handkerchief is then seen again in AG004 - You Never Can Taillow, where Ash uses it to clean Taillow’s beak.
I never noticed before, but Masaki Iwane is the animation director of all three episodes.
Masaaki Iwane is my favorite animator of the Pokémon Anime not only because his episodes look amazing, but also because he seems to enjoy little continuity nods quite a bit. Amongst other thing, he animated all three episodes where Misty’s handkerchief is seen (EP243, EP273 and AG004), the episode that show Misty and the rest of Ash’s friends watching him on TV (AG126), the episode where Ash receives the lure (AG187), and the Chronicles episode about Misty that references Ash and Brock a lot (SS002).