These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: The Mysteries Of Alfred Hedgehog
Fridge Logic: Why would so many of these animal people not know about their own species' life cycles? For example, why would 20-something year old rabbit only recently discover that he changes color in the spring? Wouldn't he have changed color every year prior to that? For the added bonus, he didn't even know what species of rabbit he was, how do you not know your own species?
Given the dialogue from that episode, and the number of other "mysteries" that turn out to be a seasonal phenomenon the kids have never seen before, it's likely that the show's Funny Animal characters have animal lifespans rather than human. If that's the case, the "20-something" snowshoe rabbit was probably only a few months old.
Hold on, pal; here's another way to think about it. maybe the funny animals age like humans and are just simple and/or stupid. One episode implies that Alfred's parents are in their forties. In addition, the rabbit has speaking parts in at least two other episodes and cameos in a few others, but he's white each time, which might make "Stranger Among Us" apocryphal. Maybe the writers didn't work out a lot amongst themselves to establish continuity.
Somewhere a Mammalogist Is Crying: In the stinger for an episode in which a raccoon has been stealing things (the stinger during the credits always gives additional facts about the natural phenomenon of the episode), raccoons are referred to as "rodents." Ooh, sorry! They're carnivores. But thanks for playing!