wow! Nice one!
Sojourner Mullein and Tefe Holland
Theodore Roosevelt and Guy Gardner
Jo Mullein is in the Green Lantern Corps with Medphyll, who is an ally of Swamp Thing, whose daughter is Tefe Holland.
Theodore Roosevelt fought beside Uncle Sam, who was defeated in Infinite Crisis by Sinestro, whose arch-nemesis is Hal Jordan, who’s in the Green Lantern Corps with Guy Gardner.
Condiment King and Dogwelder
Condiment King was arrested by Batman, who was recruited for membership in Section Eight with Dogwelder.
Collapser and Muhammad Ali
My previous Dracula attempt notwithstanding, any Collapser connection to the rest of the DC Universe is tenuous at best. No other DC characters appear in Collapser, and Collapser has never appeared in any other DC series.
Sandra of the Secret Service and Dogwelder
Sandra of the Secret Service worked for President Franklin D. Roosevelt, who chartered the JSA with Alan Scott, who mentored Kyle Rayner, who had an unpleasant evening at Noonan’s with Sixpack, who is in Section Eight with Dogwelder.
Doomsday and Bat-Mite
Negative Man and Sugar & Spike
Doomsday was killed by Superman, who matches wits every 90 days with Mr. Mxyzptlk, who (in Pre-Flashpoint continuity) inadvertently created Bat-Mite.
Peacemaker and Red Bee
Negative Man was in the Air Force with Hal Jordan, who is a client of Sugar & Spike Investigations.
Peacemaker’s Agency handler was Valentina Vostok, who was in Checkmate with Alan Scott, who was in the All-Star Squadron with Red Bee.
Stargirl and Heckler.
Heckler was once a favorite character to stymie connections, but his appearances in the recent One Star Squadron series have made connections much easier. To wit:
Stargirl was in the JSA with Power Girl, who was in One-Star Squadron with Heckler.