Just the concept of backstory Magnus and the Taaco twins being insta-besties while they were at High Stakes Adventurer Space Camp tickles me pink. They got along so well! Too well. They were the Nightmare Scenario, the Terrible Trio. Lup bridged the gap between Taako and Magnus perfectly and together they more or less wrecked havoc.
Magnus saw them on Day Three tormenting the IPRE’s equivalent to Leon the Artificer, or sneaking into the cafeteria after hours because the food was unacceptable and knew. These were his people. He attached himself to them and refused be dissuaded. Lup accepted him pretty much instantly because hello, giant person to use as a human shield/easy going goodtime fight buddy. Taako took a lot longer to warm up to their new, big, excitable tagalong, but Magnus grew on him, especially with Lup there to serve as a filter.
Of course, they were still competing for a few coveted spots on the IPRE mission, so it wasn’t all roses and sunshine. There was a fair amount of mutual pragmatism there as well. A general understanding that if it came down to it they did really want this job and would do anything to get to it. But in the meantime…. the twins helped Magnus memorize IPRE regulations, they teamed up to sabotage people they didn’t like, gave a little boost to a few select underdogs (over Taako’s protests). Lup and Magnus wrecked more training dummies than anyone could count. Playfighting in the halls. Idly using Magnus as a jungle gym to get to high shelves/look down on someone/avoid walking. A truly epic amount of foodfights. They scared off half of their fellow trainees with sheer enthusiasm (and a little bit of bullying).
Because as nice as they are, they can kind of be jerks. Lup and Magnus are good people who unfortunately have an automatic teasing instinct. Taako refuses to be a good person, especially not in such a high stakes environment with his sister already compromised. They were Space Camp Mean Girls. They were three fourth of the Marauders (Barry was their Pettigrew, obviously). They were a force of nature and juvenile hijinks. They slid in only because they had enough Bond to power the ship themselves, the three of them. They’re bad enough as Tres Horny Boys. Imagine how awful they were when it was Double the Taako and College Aged Magnus.
One of my favorite things about the Lego Batman movie is that Harley Quinn isn’t in an abusive relationship with joker, or any relationship at all really, she’s just kind of his bro who hangs out and fucks shit up with him and gives him dating advice