Last theory explored the Mail-in-Time cards and their possible origin. Let's add a new piece to the puzzle.
"Rainbow Letters" Eddie Dear Playset
dated 1971, unknown manufacturer
the envelopes are inspired by the characters
probably from an activity set based on Eddie Dear
"whoever enjoyed this playset had a grand time pretending to mail letters to their favorite Playfellow puppets!"
It's clear the last point is meant to raise questions, as it's quite unlikely a child pretended to be different characters using this many handwritings.
So for now I say these are all private letters that Wally received up to 1971, the same year the Mail-in-Time Day cards were probably made.
All that said let's go to Frank's letter, the actual focus of this post.
Three things about this letter:
Frank is very good at drawing
the envelope is not in his main colours
1) Frank is a good artist
We're used to seeing Wally as the artist of the neighbourhood. But here we have Frank depicting details of an in-universe bug, with different angles and shading, too. And that's not a one-off thing either...
Not only is Frank an artist: Wally goes to him when he needs a specific picture, such as the telephone button.
2) The envelope's colours
These are exactly the colours of Frank's house. It could solve the questions around the choice of envelope, if not for what WHRP tells us:
"This array of brightly colored letters seem to be inspired by the equally colorful neighbors of Home, such as Howdy Pillar, Frank Frankly, and Barnaby B. Beagle."
They're right about Barnaby and Howdy's envelopes. So why does Frank have his house's colours instead of his own?
That shouldn't be a note-worthy detail: Wally uses paint, Julie uses chalk, so maybe Frank is fond of coloured pencils.
Now, I ask you to follow my reasoning: it may look absurd -and it probably is- but it's essential you understand, because it's the first step of a journey. One that will try to give a timeline to Welcome Home. At least, until new updates will contradict all of this...
Let's start with the envelope. There is, in fact, a drawing that would explain the colours:
I've mentioned this picture in last theory, but I also feel the need to note that the coloured version is non-canon material. However, by choosing to use it in the ARG, Clown might have given it some purpouse, who knows...
Regarding the coloured pencils, I have to get back to what I was saying about the Valentine cards: it's possible Frank may have had a hand in their making, since a handwriting similar to his can be found on Sally's card. Maybe he did more than just writing, maybe he also embellished some of them.
Frank possibly helping Eddie with the Mail-in-Time cards in 1971 and the newspaper showing the two carrying mail together in 1969 could be a clue that the two had a different dynamic at first. Then there's the envelope that shares the same colours as Frank's 1969 image. Were those Frank's original colours, since they're the same as his house? Why have they changed, if so? And when?
I -or better, my friend and I- have an answer to that, which needs a separate post. But I'll leave a preview:
"It’s possible that Frank’s existence was ended early in the show’s run or his character had been introduced later on when creative changes took place." -WHRP