The perpetually upbeat realtor selling the Heelers’ home was hinted at in an earlier episode, and has a past with Bandit.

In “Dragon,” Bandit tells his family that he stopped drawing as a kid, even though he loved it, because another child in his class disparaged his efforts. That kid? Bucky Dunstan! (Or, as he says “Ugh. Bucky Dunstan.”) This could explain why Bandit is always so annoyed any time he has to interact with Bucky in “The Sign.”

In the Season 2 episode “Road Trip,” the Heelers forget to pack the girls’ tablets for a long road trip and they have to learn to just be bored sometimes. One of the games Chilli introduces them to is using their fingers to “jump” over objects that pass by their window, and in “The Sign” it looks like Bingo is still finding it fun as the family drives around waiting to head back to their house after it’s being viewed.

In a truly “blink and you’ll miss it” moment, Pretzel — one of Bluey’s more elusive classmates who hasn’t spoken since Season 1 — mentions his mums. This would make him the first character we know of on the series who has same-sex parents.

At the end of Calypso’s story about the farmer, Jack and Rusty enthusiastically suggest the class play army. This is a reference to the Season 2 episode “Army.” In this fan favorite, the pair are both able to grow and cope through play by pretending to be soldiers in the army. Jack, who is strongly implied to have ADHD, is able to focus better while Rusty is able to emulate his father, who is actually in the army and (as of Season 3) deployed far from his family.

As the Heeler family sets up for the wedding, Chilli, Stripe, and Bandit can all be heard singing a snippet of a song that ends in the phrase “Cat Squad!” which may be familiar.

The characters on Bluey don’t watch a whole lot of TV as far as we can see, but one show they seem to enjoy is Cat Squad, which appears to be a parody of PAW Patrol. Throughout the series you can see Cat Squad stickers, magnets, bedsheets, toys, and the occasional quick clip of an episode. True to form, the music department has written a whole theme song for the imaginary series (complete with wailing guitar solo and stylized meowing). And, true to parents, it appears that the ones on the show also get their kids’ shows’ music stuck in their head.

OK, this isn’t strictly speaking the first time we’ve seen the Heelers’ license plate on their car (aka Bobo, apparently) but it’s always fun to marvel at the cleverness of the folks at Ludo who sneak in these little details...

Initially I thought “419HLR” was a reference to April 19 and figured that was the premiere date for the series. But when I looked into it I realized the show premiered in October of 2018. After some sleuthing, Googling, and Redditing I think I found a solid theory. The hex code (which is a color code) 419fff is blue. Specifically, this shade of blue. So the license plate could stand for “Blue Heeler.” (Or I’m wrong and it has a different level of significance for the show creators and/or animators.)

In every episode of Bluey, you’ll find a hidden “longdog,” and some dedicated fans have fun trying to find it for themselves. I’ve found two longdogs in “The Sign”: one in the trunk of the Heelers car and one on the back of Busker’s laptop.

Incidentally, Chattermax, Bluey and Bingo’s loud, annoying toy that Bandit and Chilli are always hiding so they don’t have to deal with it (whomst among us, people...) is also in the trunk of the car, as well as briefly on the dance floor of Rad and Frisky’s wedding.)

Flappy the butterfly is a potent metaphor for “The Sign,” appearing in promotional materials and in pivotal scenes in the special episode. Likely, it’s meant to symbolize “the butterfly effect,” which posits that little changes early on can ultimately lead up to big differences. (Which obviously figures into the plot of “The Sign.”) But it’s not the first time we’ve seen Flappy.

Flappy first appeared in the Season 3 episode “Slide” in which Lila and Bingo play on a waterslide in the backyard but are careful to rescue a little caterpillar over and over. At the end of the episode we see that the caterpillar turns into a butterfly who revisits the pair once its hatched, landing on their joined hands.

“That’s lucky!” Bingo says as it flitters away, foreshadowing the idea of good luck and bad luck that plays throughout “The Sign.” (And highlighting the fact that the cause-and-effect chain of events we see throughout this episode began long before...)

Busker has appeared in a few episodes of Bluey. He’s been in “Markets” in Season 1, “Dance Mode” in Season 2, and is usually playing music of some kind. In “The Sign,” Busker not only officiates but DJs Rad and Frisky’s wedding. What sets this character apart, however, is that he’s based on the show’s composer, Joff Bush.

The last time we saw Bingo and Bluey’s paternal grandfather (whom, we learn, they call Bobba) was in the Season 1 episode “Grannies,” in which Bluey teaches him and Nana how to floss. (The dance, not the dental hygiene practice.) Fans have been wondering where he’s been and, happily, “The Sign” gave us an answer. But while Bobba may have been off in India “finding himself,” neither he nor Nana have forgotten how to floss, as they hit the dance floor with their signature move at their son’s wedding.

Bluey is, at its heart, all about play. Specifically, how children learn, grow, and process the world through play. In a quick moment from the wedding reception, we see her playing with the cake toppers as her parents argue in the background (not the first time we’ve seen them fight in the background, even in this episode). Whether she’s pretending the figures are Stripe and Trixie or Rad and Frisky, it’s a reminder that kids take everything in, and better understand what’s happening in the adult world through imaginative play.

Towards the end of “The Sign,” after Bluey starts comforting Bingo with the story of the farmer but before “the dogs with no eyes” spot look through the binoculars at the lookout, we see a green balloon drifting through the air. Fans might recognize this balloon from the Season 2 episode “Mum School.” In it, Bluey decides to put herself to the test by parenting a bunch of balloons. One of her children “Greenie,” is a bit more challenging than the others, and she has to take extra care to make sure he doesn’t float away. She accomplishes this by tying a little weight to his string (a green “G” magnet) but ultimately he floats out the window anyway.

“Will he be OK?” Bluey asks Chilli.

“Yeah, I think he’ll do just fine... because he’s got a good mum.”

And he is, in fact, doing great, still (somehow) floating above Brisbane...

In a sense, this is an Easter egg inside an Easter egg. Over the past couple seasons, we’ve learned through quick lines and background clues that Winton’s parents are divorced. In the background of some episodes, his dad (Cornelius) has been spotted on dates with different ladies, and in the Season 3 episode “Perfect,” looks a bit dejected in the background at a picnic, suggesting his relationships haven’t worked out. However, more recently in “TV Shop,” he and the Terriers’ mum can be seen getting friendly.

In “The Sign,” Winton references that his dad is lonely, prompting one of the Terriers to note, “Our mum likes your dad.” At the end of the episode, the “dogs with no eyes” spot a house for sale with a pool (something Winton has talked about in previous episodes), and we can see Cornelius and his new love driving off in a car together with the four kids in the back. A background little happy ending for the eagle-eyed fans who’ve been following this romance for a while!

Well, not Calypso, but Meg Washington, the singer-songwriter who provides the voice for the wise Glasshouse Primary School teacher. In the emotional end sequence of “The Sign,” as the Heelers bid a melancholy farewell to their Brisbane home, a haunting woman’s voice sings over the events. This is Washington’s song “Lazarus Drug,” off her 2020 album Batflowers. She recently told Today Extra about the experience. “Bluey‘s been changing my life since episode one, but to be a part of this amazing episode and where my song is played at the end and just how it’s been all put together, it feels like a small miracle to me.”

As the credits roll, the sky darkens to twilight and a colony of bats can be seen flying overhead. This is a sweet nod to the dreamy Season 1 episode “Fruit Bat.”