Lol, bettas are smart little buggers, and they do seem to like having something to keep them busy and enjoy a little interaction with their owners(I've found ;P). Aren't they such fun little guys? xD
None of mine ever took the the ping pong ball...xD I tried, they either freaked out or ignored it ;P Haha, perhaps I should try different colors...
You can also get some 'backup' decorations and plants...switch them out and around every week or so when you preform water changes, gives them something new to explore. ;) You can also place different little things around their tank for them to flare and stare at xD Its quite amusing.
Oh! And theres always the little floating betta mirror and betta log....those are pretty neat ;)