Happy Meal toys in Japan are assembled with tamper-resistant screws so kids can’t take them apart. The Plarail trains use a triangle screw head, so you need a triangle driver to open them. Plus/Phillips or hex wrenches won’t fit.

Which triangle driver?

• Happy Meal Plarail uses a 2.0 mm triangle screw. Many triangle bits in stores are slightly larger (2.3–2.5 mm).
• The ANEX interchangeable triangle driver 2.0/2.2 mm (No.33) works for these and regular Plarail.
• Price is around ¥1,000; cheap single-size options are hard to find at hardware stores, so Amazon was easiest.

Step-by-step: replace the batteries

1. Flip the train over and remove the two triangle screws.

2. Lift off the body to reveal the chassis; the battery box sits between the axles.

3. Take out the battery box. It uses two LR41 button cells (smaller than LR44). There’s no polarity marking—snap a photo before removing.

4. Insert new LR41 cells, re-seat the box, close the shell, and tighten the screws.

About the batteries

These toys don’t use AA like normal Plarail; they need two LR41 button cells. LR41s are tiny and often not stocked at 100-yen shops or supermarkets; online packs of 10 are cheap but may vary in quality. Remind kids to switch off the lights when storing the train—swapping these little cells is fussier than AA.

Why the triangle screw is good

Using a tamper-resistant fastener keeps small children from opening the toy or swallowing batteries. It’s the same idea as Torx security screws on playground gear. In this case, the extra bit of hassle for parents means a safer toy out of the box—nice job, McDonald’s/Plarail.