Both Matt Berry (Laszlo) and Benedict Wong (Wallace) appeared in The IT crowd together. Berry as a member of the regular cast (Douglas Reynholm) and Wong as a guest (Harold "Prime" Tong in the episode "The Final Countdown").
Topher (a dead person who becomes reanimated) is played by 'Haley Joel Osment', best known for his role in 'The Sixth Sense (1999)', where as a child he famously "saw dead people" as if they were alive.