Larch, Birch and Splinter are the three wooden boards who form as tic-tac-toe at the mines in Pajama Sam in "No Need to Hide When it's Dark Outside". They later returned in Pajama Sam 2: Thunder and Lightning Aren't So Frightening.
Pajama Sam in "No Need to Hide When it's Dark Outside"
Larch, Birch and Splinter can be found in the mine covering a disused path. Sam can use a hammer to pry the boards from the entrance to gain entry. After Sam pries the first board off, the other two give in, deciding they no longer like the job and look to find work as a floor.
Pajama Sam 2: Thunder and Lightning Aren't so Frightening
Larch, Birch and Splinter reappear in Pajama Sam 2 working for World Wide Weather on the board. They complain of not having anywhere to sit.