Grace, 31, during an appearance on Tuesday's Lopez Tonight, shared his trippy experience after accepting what appeared to be a breath strip from a female partygoer – only to find out, a few minutes too late, that it was something much stronger.
Grace said that soon after taking the substance, he asked a friend: "Is there lava coming out of the back of my head? My friend said, 'Are you okay?' and I said 'No, I think I'm fine, but I can touch colors, should I get naked?' "
Grace continued: "I did everything that I was ever trying to not do, which is too much of a cliché of someone stoned on That '70s Show."
Fellow cast member Ashton Kutcher was also at the party, but Grace said he doesn't remember seeing him. "Later he called me and said that I just said one thing to him over and over again ... I just said 'I love you, you're my brother.' "
Grace also admitted that he missed an early warning sign: The girl who offered him the breath strip suggested only taking half – advice he didn't follow.
"I didn't know what was happening," he recalled. "I said, 'Babe, I think I can handle an entire breath strip.' "