User blog comment:Kevsuc/Magnet Jelly "stops" Pet's ability? It's not always true./@comment-25854073-20141216183702

if pet activates first, then you get magnetic jelly, you get both effect

if you get magnetic jelly before the pet is supposed to activate, you only get magnetic jelly, and pet will activate right after magnetism is finished.

just think of a gauge that charges up for your pet ability, that gauge never stops. when it is filled your pet will activate its ability only if it is not in the middle of doing something else like a magnetic jelly or a bonus time.

this mechanic is important for those who are looking for maximum score and have to take every little detail into account

and example of the usefulness of this can be found in Coin Farming section: Explosive Gold Coin.