i'll take a brian cell too at this point honestly. arlo's been living with cas for the past couple of years, so they'd most likely know each other well/be close-ish by now? arlo's pretty social, enthusiastic, a lot, etc and would force everyone to have homestead type dinner parties with him while he soaks in every single pop culture reference like a desperate little sponge searching for a personality. i have to nail down an art style for his boards still, but maybe we could say that they got to talking about a board for elliot and their friendship 𝓫𝓵𝓸𝓼𝓼𝓸𝓶𝓮𝓭 from there?