"Past Transformations" name obviously refers to other transformations not included in the past episodes back in 2019. The second one features two people chatting alone when Diego off-screen decided to give them some fun. Given the skate park is built next to a nearby university campus, Diego would put the glowing radioactive tube in a dumpster afterwards for any juvenile to come across for a recyclable junk.

Dialogue has to be placed in this description instead of the drawing, as it blocks the view of these pokemorphs placed together:
Part 1
Derek: Wow Wolfa! Your skateboarding skills are so awesome!
Wolfa: Thanks, uh who are you?
Derek: Oh yeah, my name's Derek! By the way, have you heard the rumors about monsters going around this district?
Wolfa: No I haven't. I just came to Santo Tomas here to meet someone Diego Dagdag. He challenged me to a skateboarding contest. He's supposed to be here any moment now.
Derek: But what if Diego happens to be one of the monsters?
Wolfa: What are you talking about? Why does that have to do with skateboarding?

Part 2
Wolfa: Oh, you mean this? This definitely doesn't have to do with skateboarding.
Derek: One of my friends told me that such exposure to blue glowing radioactive tubes like this will force a person's body to shapeshift into any monster.
Wolfa: And this reaction also triggers muscle growth I assume. Wait a minute, I don't even see some radioactive objects around here.
Derek: Oh yeah, that. I get the feeling someone is watching us.
Wolfa: As much as I want to show our new punkish yet awesome forms off to Diego, I feel like I just came here for a trap.
Derek: It's not over yet Wolfa. I was also told that getting exposed to the same tubes while in this state may trigger transformation into another but bigger form.
Wolfa: I have two things in mind: First, this feels disconcerting to sense that you're calmly excited about this. And second, this sounds sweet, let's do this!

Part 3
Wolfa: OH YEAH!! I AM BIG AND STRONG!! YOU WITH ME BOY?!
Derek: YEAH! And you don't need to yell.
Wolfa: BUT I LOVE MY NEW ME!! Sorry I sometimes imagine myself as a bodybuilder.
Derek: Well, you look no different from a bodybuilder. You've got flames inside you, while I feel...legendary.
Wolfa: Wait, I see someone in front of us. Is that one of the monsters you told me about? He looks familiar.
Derek: Man you're right. That looks like Diego.
Diego: You're bloody right, blokes! Glad to see you've immediately embraced your new selves. Now Wolfa, wanna help me spread the mutation and turn everyone into monsters like us?

Characters (left to right):
Derek (human) --> Half-Arceus --> Arceus
Wolfa Jones (purple wolf) --> Growlithe --> Arcanine

Derek owned by  Maurili
Wolfa owned by  xpgamer12

Click here for the list of past episodes from 2019.

Early Suspicion: Part One || Two || Three || Molly Clarkson
Past Transformations: Two Sams || Derek and Wolfa || Wuschel and Wabuu
Night at Food Station: Part One (NSFW) || Two (Alt ||NSFW) || Three (NSFW) || April Fools
Tourist Attraction: Part One (NSFW) || Two (NSFW) || Three (NSFW)