The grandson from "Lost Soul" is Shawn Hunter from Boy Meets World, which Will Friedle shared top billing in.
Hilarious in Hindsight: A Batman musical? Thrown in as a joke in the episode Out of the Past, as one was being considered at the time. Fast-forward several years to a new Batman series...
I Knew It!: Some fans had speculated that Terry and Matt's parents were divorced because the boys both look nothing like their father (they have black hair, compared with Mary who is a redhead and Warren whose hair is light brown - genetically improbable). Flash forward to the Justice League Unlimited episode Epilogue which doubles as a Fully-Absorbed Finale, and guess what? CADMUS had Warren's genetic material overwritten with Bruce Wayne's, making him the boys' biological father. According to the series' staff, this decision was a Sure Why Not motivated by the realization of said genetic improbability. But fans were wrong about Terry's mom having an affair.
I Want You to Meet An Old Friend of Mine: Wil Friedle, who plays the main hero Terry, is best friends with Jason Marsden in real life, who played guest character Donny Grasso in "Hooked Up". The two actors have worked with each other in a number of other shows as well.
Barbara Gordon was voiced by Stockard Channing in Seasons 1 and 2, but was replaced by Angie Harmon for Return of the Joker and Season 3. This would not be a first for the DCAU Barbara Gordon, as she did undergo this trope twice in her Batgirl days, too.
Queen underwent this, too (having been voiced by Amanda Donohoe in her first appearance, then by Sarah Douglas in her other appearances), as did Paxton Powers (Cary Elwes, then Parker Stevenson), and Jack (Scott Cleverdon, then Nicolas Guest).
Both Zeta and Agent Bennett had different voice actors (Gary Cole and Joe Spano, respectively) in their debut episode than they did on The Zeta Project and their other appearances on Batman Beyond (Diedrich Bader and Kurtwood Smith, again respectively). Also Zeta looked completely different in the episodes after his debut in the Poorly-Disguised Pilot that wasn't.
See also Big Time, voiced by Stephen Baldwin in his first appearance and Clancy Brown in his second. Justified mostly because at the time of his second appearance he was a deformed freak and sounded different then when he was normal.
One rejected script had Terry become an item with Maxine after Dana breaks up with him, penned by Alan Burnett. Timm shot the idea down, which is unfortunate for a large part of the fandom.
Mr. Freeze's role was originally just a one-off gag appearance, where Terry was getting a soda for Bruce and, in an awkward moment, would find Mr. Freeze's head and they'd briefly stare at each other, and then Terry would close the fridge and give the soda to Bruce. This was discarded because it was an insulting and unfitting ending for his character.
While there have been reports about a rumored script for Template:Bb where Lashina and Superman's brief fling during the events of Legacy's ramifications were revealed,[1]Rich Fogel is on the record saying that "I don't recall that ever being discussed in the room at the time. The staging of the scene in Legacy clearly suggests that they were sleeping together, but whether or not anything came from that, we never really pursued that."[2] The idea seems to stem from a fanfic posted on the ToonZone forums between 2001[3] to 2005[4], which then had elements repeated in an act of wikipedia vandalism in December of 2007.[5] The falsified information remained on the page for the next 3 years until another editor noted Dwayne McDuffie had also stated the information to be incorrect in a post from his now defunct forums.[6][7]
YMMV • 
Radar • 
Quotes • (
Funny • 
Heartwarming • 
Awesome) • 
Fridge • 
Characters • 
Fanfic Recs • 
Nightmare Fuel • 
Shout Out • 
Plot • 
Tear Jerker • 
Headscratchers • 
Trivia • WMG • 
Recap • 
Ho Yay • 
Image Links • 
Memes • 
Haiku • Laconic • 
Source • Setting