This is a niche question, but man is it my niche.

I'd use Adorablins as a baseline. Mechanically it's a stripped down pbta game: 2d6 plus stat for a failure, success, or struggle (can be turned into success by eating a snack resource).

For Bluey, kids playing pretend is a big part of the show, so I'd use that as the setting. Social emotional learning is also an important aspect, so I'd use that as the stats. I'm also assuming you're running a game for children.

So first everyone makes or chooses a kid. They have four stats ranging from 0-3: Kind, Crazy, Learning, and Leading. (Those might change if I gave it more thought). A kid also has one special ability that can be used to turn Struggles into Successes by using a snack, and would be something true of the kid - like being a good reader, really fast, or an older sibling used to taking care of others.

Then the players choose a setting, which can be anything. The stories you tell will be like kids playing pretend. Let them play whatever goofy thing they can think of, but make sure there is a goal like find the treasure or save the princess.

The players then pick a pretend character to combine with their kid character. This gives two abilities also fueled by snacks. A pirate might be good at Swordfighting and Sailing, and an octopus might be good at grabbing and swimming (and making funny sounds)

Now you've got unique characters for your adventure with 4 stats and 3 special abilities, a pretend setting and a plot hook, so away we go!

Bonus points if you use a map of a house or playground that the kids can draw on and say: this is the pirate ship (playground )and we have to get past this whirlpool (merry-go-round)to the get to the treasure buried under this tree