Could be seen as just a friend thing but; Spy is nightmare prone and often wakes up in the middle of the night. When this happens he heads over to engie's workshop to see if he's still up working on a project and just hangs out with him to calm down. Engie likes the company so he doesn't mind Spy's occasional intrusions.
OOH I LOVE THIS,,, I can see Spy having bad nights where sleep isn’t coming easy, so he thinks “well I may as well have an intellectual conversation”.
He sneaks in there, promptly scares engie (throws a “Boo!” in there even), and immediately starts bugging him. Indeed Engie does like the company, even if it’s annoying company. But Spy also has such a smooth charm that engie can’t help but yearn for.
And those moments, like this one, where his guard slips just a bit and Spy lets himself be silly, happy, playful, genuine...engie falls for it everytime.
