This is something I already know, so it’s not really a TIL for me. It is however a TIR (Today I Remembered) moment, after I came across them again. 
There are three miniature cards (Turtwig, Chimchar, Piplup) from the 7-Eleven PokéBall Lottery campaign. As you can see in the bottom of this picture, they are smaller than regular TCG cards:
After seeing this, I wanted to take the opportunity to make this table with all Pokémon TCG cards I know in different sizes:
| Card type | Width (in mm) | Height (in mm) | Remarks / Picture-links |
| Regular-sized TCG card | 63.0 | 87.0 | |
| Jumbo-sized TCG card | 145.5 | 205.5 | |
| Teach Set 2000 | 86.5 | 142.5 | Link |
| Teach Set 2008/2009 | 77.0 | 107.0 | Link |
| Teach Sets 2011 (3x) | 62.0 | 86.0 | Link |
| 7-Eleven Mini | ~50* | ~65* | Link |
| Miniature Phone Charm | 19.5 | 27.0 | Link1 / Link2 |
| Tropical Present Post Card | 98.5 | 147.5 | Link |
| ‘Super’ Jumbo | 399 | 561 | Link1 / Link2 / Link3 / Link4 / Link5 / Link6 |
| ‘Ultra’ Jumbo | ~1450* | ~2000* | Link1 (Japanese ‘Pokémon Bible’ page 345) |
* I don’t have the card myself, so don’t know the exact measurements.
If you know any TCG cards of a different size, let me know. 
Greetz,
Quuador