[RPG] How to create a situation in which a PC has to make a saving throw or be forced to pet a dog

Here is how this question came up to me :

I have a dog (IRL), and it's so cute that I'm pretty crazy about it (I guess like most dog owners). My players, which are also my friends, know that.

I wanted to introduce something like an easter egg referring to it. I want to find a way to make them face a dog that is so cute that they have to make a saving throw (I don't know what kind or what DC) or be forced to pet it.

I know that as I am the DM I can just hand wave it and make it happen, but I was wondering if this can be achieved by RAW (even if it's not only because of the dog's cuteness).

So, how could a dog force a PC to make a saving throw or be forced to pet it by RAW?

• It can be the effect of an item, but you have to explain how a dog could carry this item to make it plausible.
• It can be the effect of a spell, but the spell has to be cast on the dog, not on the PCs. The saving throw must happen only when the PCs see or are near the dog. The caster should be able to leave the area after the spell is cast and the saving throw should still happen (I want the "event" to possibly happen even in a forest or else, as if the dog lost itself).
• It can also be any other effect, as long as it is RAW.
• I only have access to basic rules for now (Starter Set), so if you mention something from another official source, please quote the relevant parts of the rules.