There are only a finite number of political slogans in this world so you can forgive political parties for "borrowing" phrases from other sources.
Plaid Cymru's "Think Different" campaign has made its mark, with the party's various leaders now parroting the phrase in speeches and press releases.
They will also hope Apple's lawyers are not watching. Here's some helpful trademark advice:
8. Slogans and Taglines:
You may not use or imitate an Apple slogan or tagline.
For example: “Think different.”
Ah. My Plaid source says: "Apple who?! We actually developed ours totally independently, and then later realised Apple had used the think different part as well, honest! Great minds think alike."
They'll be claiming next to have invented a personal music player - the iPlaid? - but the great minds argument might struggle to convince Apple's learned friends. Perhaps, imitating Apple is just a core vote strategy.
As for grammar, Plaid say: "The 'Different' is not meant as an adverb - more of a statement, so the grammar is fine." That's all right then. Presumably Plaid won't be "borrowing" the full Apple script too. Here's to the crazy ones......