>>29493281>>29493342Honestly, Wally has always been super sickly. Could be he just didn't mature at the same rate. Could also be that Wally started his game way younger than the protag, which is also pretty believable considering how he's treated. I always kind of assumed he was a kid compared to the protag in RS, which would make him a kid among kids. But his constitution is probably a more believable answer.
Most of the mixed media guys took Wally's illness to be so bad the Pokemon Special writers gave him a cancer suit. Like, it's a respirator with a turtle shell style filter and some kind of gauntlet attached. Made him look like baby Bane, even by the end of RS in Special, he still doesn't take it off because he probably wouldn't die without it, but it would likely be extremely painful.
On the topic of the timeline, it's well known that 1st gen took place at the same time as 3rd. And 4th took place at the same time as 2nd. And that they were about 3 years apart. There are clues tossed in all over the third and fourth gens pointing toward it. Considering this and that the protag for 3rd is probably comparable or identical to the same age as Red (which is 11, apparently?), Wally is probably just a little younger than Red. And that's probably an objective fact. I think he's just a sickly little manlet.