It's forbidden to mention the names of foreign deities as it states in Shemoth 23:13
וְשֵׁם אֱלֹהִים אֲחֵרִים לֹא תַזְכִּירוּ, לֹא יִשָּׁמַע עַל-פִּיךָ
So mentioning Jesus or Christ is definitely forbidden.
I'd venture to say that even mentioning "Lord" and "father" would be forbidden as these prayers do not refer to Hashem but to J.C. and/or whatever else the Christians pray to.
I don't see what could be wrong with saying
"This food smells good" unless you are pretending to be praying and in fact saying something else.
That would be a problem of deceiving others, which is forbidden, and also a problem of seemingly doing something wrong, Mar'it HaAyin and possibly causing others to sin as they don't realize what you're doing.