Some TMNT stuff really isn't for little kids.
Harold Lilja is a brilliant inventor and was - together with his former wife and partner Libby Meitner - one of the top stars of the scientific community, and probably also the actual inventive brains of their duo. But when Meitner finally betrayed him and reaped the credit for Harold's work for herself, Harold became a bitter, grumpy hermit who only talked online with other intellectuals, while still hoping for a chance to rejoin the ranks of the greatest scientists. On some occasions Harold with his grumpy nature, criticized other peoples opinions, and caught the displeasure of Donatello, who had used the screename "duz_machines_84" and became Harold's silent internet-nemesis.
One day Harold was at a Expo for a chance to prove himself, but the inventions that he demonstrated there - his anti-gravity gauntlet and its cloaking device - were not yet ready, and so he got disqualified from the race. But he caught the attention of the sponsor of the Expo, Baxter Stockman, who wanted to use Harold's inventions to find the Ninja Turtles for Krang. Coincidentally Donatello was also at the Expo and had gained an honest respect for Harold's genius. When eavesdropping Donatello discovered the conversation between Stockman and Harold - and after they had recognized themselves as their respective internet-nemesis' - Harold initially objected to the turtle. But as Donatello was able to convince Harold with a few difficulties that he sincerely admired his genius and that Stockman on the other hand, would only take advantage of him like his ex-partner, Harold finally put his hatred of Donatello aside, and together they escaped from Stockman.
Although Harold was at first anything but grateful to Donatello who he said had ruined his life, the two finally reconciled in cyberspace. Later, when Donatello sought help in saving his brother Leonardo from the clutches of the Foot Clan, Harold lent him his anti-gravity gauntlets and its cloaking device which he had improved since their first meeting, and eventually he also built a battle suit and a robot ninja turtle.
Later Donatello and Harold consecrated Krangs plans to transform the Earth into a new home for his race and gave him the plans for a teleporter which the neutrino scientist Professor Honeycutt had left to fight the Utrom warlord. Harold finished the teleporter just in time to thwart Krang's conquest. When Donatello was injured in the course of this operation, Harold worked together with Honeycutt and later with the mutant Leatherhead to save the life of their mutual friend.
Later, when the Street Phantoms under their patron Darius Dun wanted to seize power in the underworld of New York City itself, Harold revealed that the phasing cloaks the Phantoms use are inventions that Meitner had stolen, and began to work on appropriate countermeasures. However, he ended up being kidnapped by the Street Phantoms and put at the mercy of Dun, whom Meitner was working for.
The Turtles and the Foot Clan successfully infiltrated Dun's compound and freed Lilja, but at the cost of injuring his estranged ex-wife. Enraged, he blamed the chaos that had entered his life on his association with Donatello, and forcefully told the Turtle to never have anything to do with him again.
By the following Christmas, Harold and Libby were living together once again. He received a Christmas party invitation from Donatello, but opted not to go.
Harold was later approached by Donatello to on the pretense of helping dismantle the Metalhead technology, after a digital duplicate of Donatello had been awakened in the robot and run amok. While initially unwilling to help him, Harold relented and let Donatello keep his technology. He later realized that the Metalhead technology would also contain a homing beacon and found Donatello with Metal-Don using the interface, which he damaged trying to protect him. Donatello then revealed that he had set up a radiation field to sabotage Metal-Don, who then attempted to strangle Donatello. Harold threatened him with a weapon of his own design and the robot commanded Harold to throw a smoke grenade that allowed him to escape. Donatello afterwards revealed that the interface had been his way of reaching out to Lilja, who in turn conceded that he had been underestimating the threats they faced and overestimating himself.
- The word "obstruse" ("obstrus") or "obtruse" ("obtrus"), which Lilja used so much, is actually a word in English but used in the wrong form. Instead, he should say - depending on spelling - either "abstruse" ("difficult to understand", "confused") or "obtuse" ("dull" or "dense")