Or perhaps they're trying to collect different ID numbers for the Jubilife Lottery and figure Caterpie's a Pokemon people are likely to agree to part with.
__________________
Elite Overlord LeSabre™
PC Vital Stats
* Pair
* PC Family * Bishies * VG Claims
* Friend Codes
Links
* Blog
* Web Site
* Fan Fictions: ★★★
* Leaf Green LP
Maybe they didn't have the National Dex yet, and wanted a Caterpie early? I know before I had my National Dex I tried to get Squirtle, Charmander, and Bulbasaur.