Captain Pike and his crew as well as the accident that crippled him are revisited
The Gateway to the past appears again
More Doomsday Machines return to wreak havoc
Kirk from the future mentions Carol Markus and her son
While the Enterprise Crew is in 2006, they watch TV - same goes for the Crew of the LEXX when they're at Prime Ridge. The Enterprise Crew find a Shuttle hidden inside a garage - in Prime Ridge is a moth (the LEXX version of a shuttle) is hidden in a garage.
DeSalle mentions flying the Enterprise through the Guardian of Forever