BKN was a syndicated cartoon block in the 90s. mostly featuring shows from DiC. there were various bumpers aired between commercial breaks that are very rare.
When "ThisTV" started airing Sonic Underground in 2010 they accidentally left the BKN bumpers intact for a while. they fixed this later on though. It's also quite possible that this happened on other BKN series that aired since 2001 (Mummies Alive, AOSTH, etc.). A YouTube channel named "baul104 luigi" has actually recorded most of them from camera in the link below.
If anybody has HQ recordings of Sonic Underground airing on ThisTV it's possible they'll have the bumpers shown in them. and it would be great to get these uploaded in HQ. continuities of BKN have always been rare.