A tear sparkled in Barbara's eye, and she reached a hand up to wipe it away. Beetlejuice seem to catch on that his wildly inappropriate behavior was even more inappropriate right now, and clammed up. 

"We've tried," Barbara said softly. "But we can't seem to make it happen." She didn't particularly want to talk about this subject with a child she just met. "Maybe that's why you found us." She smiled down at Lydia, brushing her hair out of her face. "Why don't you head to bed, sweetheart?"

Beetlejuice followed Lydia up the hall, waiting until they were in the guest bedroom before breaking the silence. "Well that was morbid," he said, crossing his arms. "And what did Babs mean by "maybe that's why you found them"? We aren't [i]staying[/i] here. This is just a temporary gig." 

Was it possible that Beetlejuice was...jealous? Afraid, maybe, that the Maitlands made insanely better guardians than he did? Which they did. Afraid that Lydia wouldn't need him anymore? That maybe he'd be forgotten when she realized how much she preferred other humans over the gross demon of highly questionable morals?