This version of Tombstone/Lonnie Lincoln gained his pale skin appearance after he fell into a vat of chemicals at the Spalding Chemical Plant. In the comics Tombstone/Lonnie Lincoln is an albino African-American who sharpened his teeth to scare his victims.
Tombstone is still working for the Silvermane family as last seen at the end of Neogenic Nightmare Chapter 12: Ravages of Time (1996)
This episode is loosely based on "The Spectacular Spider-Man" (Vol. 1) #139 and #142.
At the fight against Tombstone at Spalding Chemical Plant, Spider-Man says "You better stay still. Another swim in that chemical soup and your hair might turn green". This is a reference to DC's Joker, whose iconic green hair was the result of falling into a vat of chemicals at the ACE Chemical Plant