Huh, that's an interesting Wario's Woods reference...

[CM30]

Wario has 'bad chemistry' (aka doesn't work well in a team with) Toad in Mario Superstar Baseball and Birdo in Mario Super Sluggers.

http://www.mariowiki.com/Chemistry

Now remember who Wario was up against in Wario's Woods...

Kind of neat that the makers of the Mario baseball series remembered that, isn't it? Okay, they lost a bit of it by removing the bad chemistry between Wario and Toad in the sequel, but hey, that could be for game balance reasons.

So yeah, thoughs?

 

[warelander]

I do remember the Toad one, but I completely forgot about him having bad chemistry with Birdo in Super Sluggers,cool stuff, but given that superstar baseball was already a gold mine of Wario content it's no shock that Wario's Woods would get a little love as well.

As for Wario's and Toad's chemistry changing (from an in-universe perspective anyway, out of universe it's probably really just for balancing purposes) :
I always liked to think that Wario was being a good samaritan by dropping his grudge against Toad, it's not like they had a big fight like in Woods ever again and heck, the little dude gave him a friggin' star constelation for his birthday:

So it's safe to assume that Wario abandoned the hard feelings against him at one point, althought I do wonder what chemistry they would share nowadays with Toad beeing a treasure hunter now...

 

[Wario Man]

Wario is proud of you.