Do you remember waaaaayyy back in last summer when I talked about how Rocky was pretty much friendless as a colt? Weeelll, that wasn't entirely true…
1. It'd be an understatement to say that Petri and Rocky were destined to be friends. I mean, Pinkie pretty much planned out their friendship before the two were even born, so it's not like the Colts had much of a choice. I'm talking ̶m̶a̶n̶d̶a̶r̶t̶o̶r̶y̶ weekly play dates, ̶f̶o̶r̶c̶e̶d̶ encouraged activities for just the two of them, pairing them up in any situation possible including trivial seating arrangements, and even hosting double birthday parties for the two, just in case it hadn't been quite hammered into them that they were the same age and relatives and that meant they should be friends already consarnit-.
But despite her over-the-top antics and meddling ways, the two cousins somehow managed to form something of a friendship together. Although Pinkie usually takes the credit for it, the truth is that Petri naturally drew to Rocky's calm and quiet demeanor. However, because they were rarely seen apart and their friendship was expected, everyone naturally assumed they were friends, as did the two colts. That is until Petri found himself asking, gee, was Rocky his friend or was Rocky just tolerating him because he had to? These doubts nagged at him to the point where he couldn't take it anymore and just had to know. Fortunately, Rocky's answer emotionless as usual, was still enough to put Petri's mind at ease and for the first time, he felt the fuzzy feeling of friendship.
2. Contrary to common belief, Petri will once in a while venture out from his hermit-cave-like-home and into normal pony society, although it's usually just to accompany Maud on her grocery trip. During one of said shopping expeditions, Petri wandered off for the thirtieth time only to return a minute later at a slightly faster pace than usual with glasses fixed firmly between his bucktooth grin. It didn't matter to Petri that he had perfectly good eyesight- if Rocky wore glasses, then he was determined to wear one as well! Maud eventually consented on the condition that a fake pair would be bought to replace the real ones. If you think he looks dorky now with his plastic glasses and protruding overbite, just wait until he gets braces.
3. Despite only being about a day younger from Rocky, Petri looks up to his cousin as if he were years older than him- which isn't surprising, considering Rocky acts unnaturally mature for his age. It should also come as no surprise that Petri, who's IQ is around room temperature, idolizes Rocky's extensive knowledge and problem-solving skills. He doesn't care that he can't understand the big, hard-to-pronounce words Rocky uses, if it sounds important, then it must be important- and by default, so is Rocky. Even the homemade 'sciencey' projects and contraptions seem to him like the next best thing since bug catchers.
Of course, Rocky can't help it if Petri's admiration of him inflates his ego just a little bit. I mean, for once somepony actually likes his 'boring-sciency-stuff' and doesn't think he's a 'stuck-up-stick-in-the-mud.' Can you really blame the guy if he shows off once in a while to his impressionable, gullible cousin? Besides, it's not like he lets the pride enlarge his head too much that he starts belittling Petri because of it. On the contrary, he instead feels something like pity deep, deep down for him and in his own apathetic way, he took Petri under his wing in an attempt to help his weaker minded cousin become smarter. The results have been…sparse so far, but Petri remains as obviously optimistic as ever.
4. Even though Petri was the one and only soul that Rocky could tolerate and maybe on a good day possibly like, there were days when Petri grated his already narrow nerves. For as much his dimwit cousin understood the meaning of personal space, the word 'solitude' or 'clingy' didn't exist in his limited vocabulary. Don't get me wrong- Rocky doesn't mind him hanging around or rambling on about his bugs; but if there's one thing Rocky despises, it's being interrupted while he's reading. Unfortunately, Petri tends to do often. It doesn't help matters that Rocky's knee jerk response is sarcasm, another thing that bounces off his cousin like a feather. On the bright side, Rocky can tune out his cousin's stutter filled reading without him knowing.
5. Unlike most normal ponies, who find Petri's unnatural obsession with creepy-crawlies unsettling at best and freaky at best, Rocky doesn't mind at all. Not because he likes bugs and the such, in fact- while he's not afraid of the little critters, he prefers to be indoors where it's comfortably air-conditioned, rather than out in the hot steamy weather where the gnats and mosquitoes would distract him. However, if Petri is passionate about insects, then who is he, an anti-social, hermit-like nerd, to judge? Even if he finds his cousin's insect books childish and his ideas of 'certain bugs bringing good luck or wishes' even more so, he merely rolls with it all for the sake of his odd, but endearing cousin.
6. Besides doing things like sitting quietly in a corner while each one does his own activity and staying up past bedtime to finish a chess game, the two colts both enjoyed another pastime: playing with their inanimate pets. Of course, when your pets are a mushroom and a rock, there's not exactly much playing going on. Still, that doesn't stop the two from having fun just talking about their pets. Sometimes, they'll even go so far as to take Cliff and Bella out for some fresh air on a fall day, maybe sunbathe a little, and have a little picnic while Rocky reads A Treatise of the Reflexions, Refractions, Inflexions, and Colours of Light aloud. Ah, the good ol'e days.