So, I just read this articles about Pokemon moves, Celebrate and Hold Hands.
Both of them introduced in Generation VI Pokemon games and does absolutely nothing. Both of them also shares this trait with Splash move that introduced from Generation I.
But not like Splash, both moves are event-exclusive move. Splash introduce because it have some related Magikarp that said it only can splashing around.
People will remember Magikarp if we're talking about Splash and vice versa.
So, how about Celebrate and Hold Hands? Are they have related with some event (in Pokemon of course) or they're just… umm… useless moves?
Best Answer
Whilst they seem to have no tangible benefit in-battle, Omega Ruby and Alpha Sapphire's Contests is another matter:
Unfortunately after extensive research I was unable to find any evidence that definitively proves or disproves whether Hold Hands has any effect on Pokemon's Happiness.
Until we can see some in-game testing or a trusted source that definitely lists it as proven or disproven I think the jury is still out on this one.
The other rumor that was floating around was that it boosted Happiness-based moves (i.e. Return), however this has been disproven, it provides no immediate benefit in-battle.