Last post I covered crossovers on the same network and same night, now I am covering crossovers that happened between different networks. This rarely has happens as networks compete but mostly happens as they are from the same producer.
Fox's Ally McBeal/ABC's The Practice (1998)
Since David E. Kelley ran these two shows and they were both hits, ABC and FOX agreed to cross them over. On the night of April 27, 1998, Ally McBeal‘s episode "The Inmates,” Dylan McDermott appeared and an hour later on ABC, Calista Flockheart and Gil Bellows appeared on "The Practice" episode "Axe Murderer."
WB's Angel/UPN's Buffy (2003)
Buffy was on the WB but then UPN for Seasons 6 and 7 in 2001-2003. Season 3 of Angel and Season 6 of Buffy had no on-screen crossovers but off-screen, which was played with in the comic books (Dawn, Anya and Xander wondered about the Buffy/Angel encounter). While it did NOT happen on the same night and not crossover many characters, the characters did crossover and bridge a recurring character over. Season 4 of Angel episode "Orpheus" aired March 19, 2003 where Alyson Hannigan (Willow) guest starred and took Eliza Dushku (Faith) with her. Faith reappeared on Buffy on Season Seven's episode "Dirty Girls" which aired on April 15, 2003. Though Willow did get a phone call from Fred in the episode "The Lies My Parents Told Me" which aired March 25, six days after "Orpheus" aired so if Buffy fans didn't know about the crossover and found out through the Buffy show itself, then they would've missed the episode. David Boreanaz (Angel) later appeared on "End of Days" and "Chosen" of Buffy on UPN while his show was still airing on the WB.
This character has crossed over networks and genres. He has originated on NBC's "Homicide: Life on the Street," (1993-1999) and when that show was canceled, he later moved on to NBC's "Law & Order: SVU." While he was on Homicide he guest starred on Law & Order in 1996 four times. John Munch has been on SVU since it started in 1999. While he was on "Homicide," he appeared in FOX's sci-fi classic "The X-Files" in 1997 with the Lone Gunmen. In 2000, he appeared on UPN's "The Beat", which was canceled in months. In 2005, he appeared on "Law & Order: Trial by Jury" on NBC. He then appeared on FOX's comedy Arrested Development's season three episode "Exit Strategy" in 2006. In 2008, he appeared on HBO's The Wire's episode "Took." He has also made guest appearances on other types of programs like "Jimmy Kimmel Live!" and "30 Rock" (but as the actor himself Richard Belzer).