My thoughts exactly!
I agree 100%!!! Not only is that a great idea, but it would be so quick, and subtle, that it wouldn't break Timm's rule of continuity references getting in the way of great storylines!
And, like you said, who said that the characters' brief appearances have to have anything to do with the storyline? Just show Alfred in the background, dusting the Batmobile, while Batman is in his cave and at his computer talking to the other JL members in the Watchtower, etc.
Why can't Timm & Co. do this? It's so simple!
Favorites! (1) Action: Transformers & G.I. Joe; Visionairies; The DCAU; Robotech, DBZ, Cowboy Bebop, Samurai Champloo & Trigun; TMNT, MOTU; and Avengers: EMH; (2) Comedy: The Simpsons & Futurama, Space Ghost: Coast to Coast & The Brak Show, Sealab 2021, Harvey Birdman: Attorney at Law, ATHF, The Boondocks, The Venture Bros., and Archer