An episode had Nigel delirious from a stonefish sting waiting for Eliza to return with antitoxin. In his delirium, he mistakes a passing catlike creature for his wife, picks it up and tells it how much he loves it and the children — then kisses it. Supposed to be funny, but it becomes more of an "Aaawww..." moment when you realize that he knows these could be his last moments and his thoughts turn to her.
In "The Origin of Donnie," after learning the whole truth about him, each of the Thornberrys talks to Donnie — seeming like an overall "welcome to the family" speech. There is also Donnie's drawing shown during the TV-Movie. It turns out that his crude drawing is actually of his parents, showing that despite his wild boy tendencies, he still remembers them.
What about the official acceptance? Nigel and Marianne are so overcome with emotion that they can't say more than one word. Debbie then takes up the speech by saying in her normal tone "What they're TRYING to say is that out of all the jungle boys we could've found..." She then bursts into tears and walks off. Then to cap it off, Eliza walks up to the confused Donnie and gently says one sentence: "We're glad we found you."
In the movie, Eliza gives up her powers to save her sister.
In "Look Who's Squawking," Eliza puts Darwin in charge of a penguin egg while she runs off to assist the parents. She comes back to find him singing gently to it and very much opposed to giving it up, even breaking down in tears when he watches it hatch. At the end of the episode, the parents name the chick Darwina.
The episode "Forget Me Not".
Nigel keeping Eliza from freezing to death through sheer badassery.