Rose smiled a little, nodding. The whole thing was still sort of assumed. She didn't mind. She trusted him with everything, but she knew it couldn't all rely on her trusting him. She didn't want him assuming responsibility for this, in case something went wrong. It couldn't all be his fault, until the end of time. She didn't want either of them blaming him down the road.
"So what you're saying is:" She took on his accent, or the closest impression she could do, "Rose Tyler, I love you and I promised you forever. I've come up with this incredibly complicated science-y plan, now it's up to you. Do you want to drink my banana-flavored elixir?" She couldn't help a small smile, in spite of the seriousness she was trying to affect. "Are you ready for forever?"