Johnny Galecki was totally ready to stand in for Kaley Cuoco's mini horse at her wedding

Up until now, we were pretty sure that Kaley Cuoco's wedding in June to Karl Cook had gone off super-smoothly.

But as Cuoco's "Big Bang Theory" co-star Johnny Galecki — whom she once dated and is married to on the show — revealed on "The Late Late Show" Thursday, there was one tiny glitch.

"(Cook and Cuoco are) massive animal lovers, and they had their animals there," he told James Corden. "I found out today they have a miniature horse they were trying to get to walk down the aisle."

Corden knew immediately that the mini-equine's name was Smooshy; Galecki confirmed the creature had its own Instagram page.

Alas, as he revealed, Smooshy was not on board with going down the aisle.

"Why?" asked fellow guest Joan Collins.

"Because he's a horse!" Corden laughed.

Galecki, 43, and Cuoco, 32, dated quietly for about two years, and she spoke about it in 2016 as a "wonderful relationship." This is Cuoco's second marriage; Galecki hasn't been married, but introduced the world to his new girlfriend Alaina Meyer, 21, on Instagram earlier this week.

"Big Bang Theory" is set to end its 12-season run next year, perhaps with a resolution to the long-running broken-elevator gag.

As for Cuoco's wedding, despite the horse refusal, "Everything went smoothly," Galecki assured. "I thought, well, I would have gotten in a miniature horse costume for that. I'm out of a job come April!"

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