Help me come up with effects for an alchemist's magic mushrooms

[PhoenixPhyre]

So I ended up ad-libbing a portion of a game recently and a player ended up with a large collection of what I described as "assorted mushrooms of fantastic looks (rainbow colors, glowing in the dark, etc)" from the deserted, ruined tower of an alchemical savant of ages past. I'd like to be able to tell the player what happens when they inevitably try a few, but am lacking in ideas.

What would a slightly crazy alchemist grow magic mushrooms to do? How could they have changed over several hundred years of neglect and cross-breeding?

If it matters, the system is 5e D&D but in a custom world and I'm not afraid to brew some things up if needed. I mainly need ideas.

[Vitruviansquid]

A few of them should just outright kill you, and you'd need some kind of investigation skill to figure out which ones.

A classic staple of the fantasy genre would be to have one make you grow to giant-size and another shrink you.

A particularly nasty one might seem to grant the user incredible powers - flight, super strength, confidence and charisma, speed, fire breath, laser vision. The key words there are "seem to." It actually just gives the user hallucination and a feel-good high that causes them to think they have these things.

[PhoenixPhyre]

A few of them should just outright kill you, and you'd need some kind of investigation skill to figure out which ones.

A classic staple of the fantasy genre would be to have one make you grow to giant-size and another shrink you.

A particularly nasty one might seem to grant the user incredible powers - flight, super strength, confidence and charisma, speed, fire breath, laser vision. The key words there are "seem to." It actually just gives the user hallucination and a feel-good high that causes them to think they have these things.

I like the grow/shrink ones and the hallucinations. This is a relatively low-key game, so I think I'll pass on instant death. I'd probably go for a few days or so of coma.

The one who picked them is a druid with Nature proficiency, so I'll let her make some checks to figure things out before actually tasting them. I figure some of them will simply be good tasting--even crazy alchemists need flavorings for food.

At least a few should be beneficial--another player got a pseudodragon pet/familiar from that same lab.

[Magentamist]

Just gonna throw out ideas:

-Grant the player knowledge of another language, or make them lose one of their own languages. If you're feeling mischievous, the character could think they know the language but actually be spouting gibberish or saying something entirely different.

-Grant the character use of a cantrip for some time, but make them lose a hit point every time they cast it.

-Grant the character inspiration

-Make the character see/hear a spirit. This spirit could give guidance, try to get them to do something, hinder them, pass on a message/warning, etc.

-Several mushrooms with similar markings that, when combined, can make something beneficial like a potion.

-Grant the character a sort of "spider sense" that warns them of danger nearby. How accurate the sense is... well, that could change things a lot.

[Recherché]

-Temporarily de-age the consumer back to teenager-hood

-Give them visions of another place or time

-Hangover cure.

-Turn the water into a giant mushrooms based monster for a short time

-Make them glow in the dark, acting as a light source for the party. Too bad it makes stealth almost impossible.