1) Warm the bench
-James is not content just warming the bench, so he left to play for a smaller club.
-Gary was always a bench warmer at the bowling competition.
-Heidi was a bench warmer on the basketball team, and plotted to poison the star player.
Definition: to be a substitute, or a secondary participant
Etymology:This expression comes from such sports as baseball and football, and their standard practice of having substitute players sit on a bench in case they are needed in a game.
2) Down that rabbit hole
-Do not date Alisha, she will drag you down a rabbit hole.
-Because Adam refused to let his parents pay his tuition, he got sucked down a rabbit hole of unpaid student loans and bad credit scores.
-Let us not discuss religion and politics at the dinner table, we will be sucked down a rabbit hole.
Definition: a way into a bizzare world, or something complicated without a resolution
Etymology: This expression comes from such sports as baseball and football, and their standard practice of having substitute players sit on a bench in case they are needed in a game.
3) Thick as thieves
-Before the car accident, the two friends were thick as thieves.
-Ivan and Monica were thick as thieves, they go everywhere together. Maybe they are dating.
-Those two families are thick as thieves, that they made their kids get married.
Definition: closely nit, tight